The fight for the besieged southern port city of Mariupol has entered its final stages, as Russian troops advance on the city's center after a nearly two month-long blockade. 

Here are the key events in the battle for the strategic city.

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February 24: Russia launches military assault on Ukraine, which it calls a "special operation" to "denazify" the country. Its forces move towards Mariupol from parts of eastern Ukraine controlled by Russia-backed separatists.

March 1: Mayor Vadym Boychenko says the city has been shelled for five days.

March 2: Boychenko says the city lost power and has no running water or gas. Russian forces, who say the city is completely surrounded, are allegedly blocking civilians from leaving and bombing densely populated civilian neighborhoods. Moscow says it is not targeting civilians. Local authorities later pinpoint this day as the start of Russia's blockade.

March 4: The mayor says the city is running out of food, appealing for a humanitarian corridor to evacuate some of its 400,000 residents.

March 5: Moscow and Kyiv reach a partial ceasefire agreement to open a humanitarian corridor from the city. Both sides blame each other as the ceasefire collapses.

March 6: An advisor to the mayor claims people are "drinking from puddles" due to the loss of running water caused by Russian bombardment. He adds that there is no heat or electricity.

March 7: The U.S. ambassador to the Organization for Security and Co-operation in Europe describes two attacks on Mariupol as "war crimes", claiming Russian forces bombed evacuation corridors while civilians were using them.

March 9: Russian forces are accused of bombing a maternity hospital. Four people are reported dead, one of them pregnant. Despite photographic evidence, Russia claims the hospital had no patients.

March 12: Ukraine's military says that Russian forces have captured the city's eastern outskirts.

March 13: The city council announces that the last supplies of water and food are drying up. Boychenko says Russian forces have bombed the city at least 22 times in 24 hours. 

March 14: The first convoy of evacuees is allowed to leave Mariupol in private cars after a humanitarian corridor is agreed. Around 2,000 civilian cars leave the city in a 24-hour period. 

March 16: Russian is accused of bombing Mariupol’s Drama Theater where hundreds are sheltering. Moscow denies responsibility. It is later estimated that 300 people were killed.

March 18: Russian forces enter the center of Mariupol, prompting heavy fighting. Ukraine says more than 350,000 people remain under siege there, with no access to food or water.

March 19: Kyiv claims Russia is using civilian evacuations to illegally deport Mariupol residents to Russia. Heavy fighting begins at the Azovstal steel plant.

March 20: Ukraine accuses Russia of bombing a school in Mariupol where an estimated 400 women, children and elderly people were sheltered.

March 21: Moscow gives an ultimatum to Ukrainian forces in Mariupol to surrender, offering safe passage from the city. Kyiv rejects the proposal. EU foreign policy chief, Josep Borrell, calls Russia’s attack on Mariupol "a massive war crime".

March 23: Local authorities, including the mayor, leave the city due to deteriorating situation.

March 24: Mariupol authorities accuse Russia of illegally deporting 15,000 people.

March 27: Boychenko says Ukraine is still in control, but Russian forces have entered the city's center, adding that Mariupol needs a "complete evacuation".

March 28: Officials say that nearly 5,000 people have been killed since the start of the siege, while around 290,000 have left the city. It adds that around 90 percent of the buildings have been damaged and 40 percent destroyed. Russian forces seize the Azov Battalion's military headquarters. "We are in the hands of the occupiers today," says the mayor.

March 30: Street fighting is heavy and Russian forces control half the city, a Ukrainian presidential adviser says.

March 31: The International Committee of the Red Cross  (ICRC) confirms Russia has agreed a humanitarian corridor from the city, with Ukraine sending buses to evacuate civilians. 

April 1: A mayoral aide says the city remains closed, and is "very dangerous" for anyone trying to leave. The International Committee of the Red Cross (ICRC) tries to lead a convoy of buses and cars out of the city, but are turned back. Donetsk's governor accuses Russia of breaking its promises to allow aid into the city.

April 2: The ICRC says its operation to help people leave continues, despite Moscow saying it failed, blaming it on the organization's "destructive actions". Ukrainian forces including regular troops and members of the far-right Azov Battalion militia continue to hold off Russia's assault.

April 3: Zelenskyy says Russian forces are aiming to seize the country's south-east, praising forces defending Mariupol for allowing other cities to gain valuable time. 

April 4: A Red Cross team is unable to reach the city to evacuate civilians due to security conditions. Ukraine accuses Russian forces of blocking the ICRC's evacuation efforts. Moscow backs a self-proclaimed mayor of Mariupol who is collaborating with Russian forces.

April 5: Zelenskyy says Ukraine's efforts to push back Russian troops from Mariupol are facing difficulties. France opens an inquiry into possible war crimes in the city. Civilians are allegedly only able to flee on foot or by private car.

April 6: Russian air strikes and heavy fighting continue. British military intelligence warns that the humanitarian situation is worsening: "Most of the 160,000 remaining residents have no light, communication, medicine, heat or water."

April 7: Greece says it will ask the International Criminal Court to investigate alleged war crimes in Mariupol.

April 8: The governor of Donetsk says it has not been possible to get any humanitarian aid to the city.

April 11: Kyiv says Russia will begin an offensive soon in Donbas, with Mariupol as its main target. Ukrainian forces say they are preparing for a "last battle" for the city because ammunition is running low. Separatist forces claim to have captured 80 of Mariupol, while an estimated 100,000 remain stranded there. 

April 12: Ukraine says it's checking unverified information that Russia used chemical weapons in Mariupol. Donetsk's governor Pavlo Kyrylenko says Russian forces are not allowing residents to leave.

April 13: Moscow says that more than 1,000 Ukrainian marines have surrendered as it intensifies its campaign in Mariupol. The mayor says the civilian death toll is estimated at around 21,000.