MAIN HEADLINES

• Ukrainian President Volodymyr Zelenskyy has accused Russian forces of seizing a humanitarian convoy west of Mariupol, adding that 100,000 people remained in the city living "in inhumane conditions."

• Russian forces have entered Mariupol, according to a senior US defense official, with local authorities reporting two "super-powerful bombs" hit the besieged city on Tuesday.

• An agreement had been reached to try to evacuate civilians trapped in Ukrainian towns and cities through nine "humanitarian corridors", but the deal does not include a safe corridor from Mariupol.

• The governor of Ukraine's Luhansk region has said a local ceasefire deal has been secured to evacuate civilians trapped by fighting.

• Kremlin spokesperson Dmitry Peskov has refused to rule out the use of nuclear weapons in the case that Russia faced an "existential threat", a statement later condemned by the Pentagon. 

• Russian Foreign Minister Sergei Lavrov has warned that the presence of a peacekeeping mission in Ukraine would lead to a "direct clash" between Russia and NATO.

• U.S. President Joe Biden is flying to Europe for an emergency NATO summit on Ukraine, where Zelenskyy will speak virtually to Western politicians.

• About 300,000 people in the occupied southern city of Kherson, the first major Ukrainian city to be captured by Russia, are running out of food and medical supplies, Ukraine’s foreign ministry has said.

• Kyiv has said Russian forces are using the exclusion zone around the defunct Chernobyl nuclear plant to prepare new attacks.

• Russia's Defense Ministry said Russian forces had used long-range weapons fired from the sea to hit a Ukrainian arms depot outside the northwestern city of Rivne.

• Kyiv officials said two civilians were killed in overnight shelling in the Mykolaiv region, while residential buildings and a shopping mall were struck in two districts of Kyiv, injuring at least four people.

• A senior U.S. defense official has said Russia's combat power in Ukraine has declined below 90 percent of its pre-invasion levels, despite Russia saying its "special military operation" in Ukraine is going to plan.

• The Pentagon says Ukrainian soldiers are successfully fighting back against Russian forces to reclaim ground in some parts of the country.

• China's foreign ministry has said that no G20 member has the right to remove any country's membership in response to threats to bar Russia from the international forum.

• Poland's security service has identified 45 Russian diplomats as suspected spies and called on the foreign ministry to expel them.

• The head of the International Committee of Red Cross is in Moscow for two-day talks with senior Russian officials and will raise "pressing humanitarian issues" in Ukraine.

• The EU is due to set out plans on Wednesday for providing jobs, education and housing for refugees.

• The US government is developing plans to impose sanctions on members of the Russian parliament, with the measures expected to be announced Thursday.

IN DEPTH

On the ground

After failing to secure swift gains four weeks into the Ukrainian conflict, Russian forces appear to be turning to "a war of attrition" with devastating effect on major cities and their civilians.

The US government says Moscow has intensified its aerial and naval bombardment as its land advance stalls. Russia's attacking forces remain 15 kilometres (10 miles) away to the northwest of the Ukrainian capital Kyiv and 30 kilometres away to the east.

Capturing Kyiv had appeared to be the Russians' top target as they entered the country on February 24, hoping to topple Zelensky's administration. However, Moscow has only taken one major urban center - Kherson in south Ukraine.

US Defense Department spokesperson John Kirby told CNN on Tuesday Russians were losing morale as food and fuel run out, while Russia is yet to solidify its control of the skies over Ukraine.

However, the southern city of Mariupol remains subject to intense siege, with more than 200,000 people trapped inside and Russia's seemingly indiscriminate bombing campaign prompting Western outcry. Russian troops reportedly entered its city center for the first time this week.

Other major cities like Kharkiv, Ukraine's second-largest urban hub and strategic Mykolaiv, on the road to Odesa, are also under constant bombardment. However, Western officials say there was poor coordination between ground and air forces.

"The Russian lack a real command and control policy," a former top French military officer told AFP.

The number of soldiers killed cannot be verified, although the Pentagon claims as many as 7,000 Russian dead in the first month, more losses than the US suffered in its occupations of Iraq and Afghanistan combined.

"Putin's offensive is stuck despite all the destruction that it is bringing day after day," German Chancellor Olaf Scholz said Wednesday.

"The more the Russian infantry struggles, the higher the army climbs up the scale of brutality and the disproportionate use of air power," a European source close to NATO told AFP. "Putin needs a deal, so he needs victories," they added.

Western analysts have warned against pushing Kyiv into accepting a ceasefire prematurely, saying Moscow could use a break in the fighting to build up forces.

Lavrov claims U.S. stalling talks

Russian Foreign Minister Sergei Lavrov has accused the U.S. of seeking to disrupt Moscow's talks with Ukraine aimed at ending the almost four-week-long conflict.

"The talks are tough, the Ukrainian side constantly changes its position. It's hard to avoid the impression that our American colleagues are holding their hand," Lavrov told students at the Moscow State Institute of International Relations on Wednesday.

He went on to claim that it was disadvantageous to Washington for an agreement to be achieved quickly, accusing the U.S. government of wanting "to pump up Ukraine with weapons."

The U.S. "apparently wants to keep us in a state of military action as long as possible," the Russian minister said.

U.S. President Joe Biden arrives in Europe today for an emergency NATO summit, his first trip abroad since Russia launched its military operation in Ukraine. 

He is set to meet NATO and European leaders in an emergency summit at the Western military alliance's Brussels headquarters, with additional sanctions against Russia expected to be announced on Thursday. 

Ahead of his trip to Europe, Biden claimed that Putin's "back is against the wall", after Moscow has so far failed to capture a major Ukrainian city while Western sanctions have essentially cut it out of the global financial system.  

However, Lavrov said that Moscow needed to "stand firm", going on to accuse Kyiv of "back[ing] away from its own proposals" and stalling peace talks, which started last week.

Ukraine has said it is willing to negotiate but will not surrender or accept Russian ultimatums. Zelenskiy said in an overnight address the talks were "very difficult" and "sometimes confrontational," but added that they were moving forward.

A New West-Russia flashpoint?

During his trip, Biden will also visit Poland, which apart from taking in the majority of the more than 3.5 million Ukrainians fleeing the conflict, serves as a key route for Western weapons to Ukraine.

Tensions have grown between Warsaw and Moscow since the Ukraine conflict escalated, with analysts expressing concern that Poland could become a new flashpoint for Russia and the West.

In his address, Lavrov referred to "provocative statements" about Soviet-era MiG fighter planes - seemingly referring to Poland's rejected offer to send its MiG-29 fighter jets to Ukraine via a US air base - and Kyiv's calls for extra Stinger missiles.

"Western countries want to play some kind of intermediary role but we have red lines," said the minister.

A day ahead of Biden's visit, former Russian president and prime minister Dmitri Medvedev accused Warsaw's "mediocre politicians and their puppeteers from across the ocean" of sacrificing the interest of Polish citizens to Russophobia.

Warsaw is now seeking to expel 45 Russian diplomats after saying last week it would call for a peacekeeping mission in Ukraine at the next NATO summit, a move the U.S. has ruled out.

"I hope they understand what they are talking about," Lavrov said of Warsaw's proposal.

"This will be the direct clash between the Russian and NATO armed forces that everyone has not only tried to avoid but said should not take place in principle."