Belarusian president Alexander Lukashenko said on Monday he would be willing to hand over powers after a referendum, as he attempts to pacify mass protests and strikes amid growing demands for his resignation.

He presented the offer after exiled opposition politician Sviatlana Tsikhanovskaya said she was willing to lead the country, but Lukashenko insisted he would not do so while under pressure from demonstrators.

Read more: Lukashenko "is almost over" and can't rely on Russia: Moscow academic

Lukashenko's statement comes after Russia stated it was prepared to provide military assistance to Belarus in the event of an external threat. 

Moscow's intervention was noted by EU leaders planning to hold an emergency video meeting on Wednesday to discuss the crisis, as growing demonstrations continue to give the longtime leader his greatest challenge yet. 

In a sign of Lukashenko's precarious position, he was heckled during a speech to workers at one of the large state-run industrial plants, considered to be the seat of his core support base, as demonstrators amassed at the factory.

"We held elections already. Until you kill me, there will be no other elections," he said, according to Tut.by media outlet. He did offer to change the constitution, but this concession appears unlikely to satisfy protesters.

Read more: Belarus releases 2,000 protestors but denies abuse

According to workers at the Minsk Wheel Tractor Plant, several thousand staff had walked off the job, with footage emerging of workers from other plants marching to the factory to join the protest, part of a call from opposition leaders for a general strike.

"We'll put the changes to a referendum, and I'll hand over my constitutional powers. But not under pressure or because of the street," Lukashenko said, according to the official Belta news agency.

"Yes, I'm not a saint. You know my harsh side. I'm not eternal. But if you drag down the first president you'll drag down neighboring countries and all the rest."

However, the leader was reportedly heckled by the crowd. "Thanks, I've said everything. You can [continue to] shout 'step down,'" he said, after struggling to be heard.

Newcomer for next president?

The president's speech came the day after Minsk held the largest protest rally in Belarus since Lukashenko took power in 1994, with estimates that more than 100,000 people had joined the anti-government demonstration. 

The unrest has also spread to those normally seen as loyal to the president, as workers from large state factories staged walkouts and the anti-Lukashenko movement was reported to have been bolstered by an ambassador, some members of the police force and journalists from state media.

The main challenger in the contested presidential election on 9 August, Svetlana Tikhanovskaya, announced on Monday she was prepared to take over the country's leadership, saying she was "ready to take responsibility and act as a national leader during this period."

Tikhanovskaya – who calls herself "an ordinary woman, mother and wife" – ran in the presidential elections earlier in the month after some other potential candidates, including her husband, were jailed.

Tikhanovskaya had announced the creation of a Coordination Council to ensure a transfer of power, asking foreign governments to "help us in organising a dialogue with Belarusian authorities." However, until Monday it had been unclear if she would be prepared to take control herself. 

In the video she said she would do so "in order for the country to calm down... so that we release all political prisoners and as soon as possible prepare the legal framework and conditions for organising new presidential elections."

Russian assistance and EU pressure

On Sunday, Moscow said that president Vladimir Putin had told Lukashenko he was ready to offer Belarus military assistance in the face of external pressure. 

This would be provided "if necessary" through the CSTO military alliance between six ex-Soviet states, according to the Kremlin.

Read more: Belarus turmoil: Does Russia still support Lukashenko?

In response, EU leaders will hold emergency video talks on Wednesday to discuss the crisis and are expected to send a message to Russia to stay out of Belarus.

"The people of Belarus have the right to decide on their future and freely elect their leader," European Council president Charles Michel tweeted. "Violence against protesters is unacceptable and cannot be allowed."

The decision follows an agreement from EU foreign ministers on Friday to draw up a new round of sanctions in response to the crackdown, with Germany on Monday saying it was ready to back even tougher measures.

NATO's secretary-general Jens Stoltenberg said on Monday that the alliance remained vigilant about events in Belarus and it posed no threat to Minsk, but was ready to protect its allies.