In his latest Facebook video address, the Ukrainian president said: “All wars end in agreements. Meetings continue. As I am told, the positions in the negotiations sound more realistic.”

Russia has continued to pressure Ukraine to formally renounce its intention to join Nato and formally recognise the separatist provinces of Donetsk, Luhansk and Crimea.

At least two people were injured as shell fragments hit a residential building

Putin accused Kyiv of “not showing a serious commitment to finding mutually acceptable solutions”, according to the Kremlin’s account of a call with Charles Michel, leader of the EU Council.

Zelensky said yesterday that Ukraine had to accept that the “door of Nato” had closed.

As diplomatic efforts to negotiate a ceasefire were increased, Zelensky told a meeting of the northern European security coalition’s joint expeditionary force: “Of course, Ukraine is not a member of Nato. For years we have been hearing about the alleged open door, but we have also heard now that we cannot enter. This is true, and it must be acknowledged. I am glad that our people are beginning to understand this and rely on themselves and the partners who are helping us.”

Ukraine’s refusal to rule out joining Nato has been one of President Putin’s pretexts for going to war. It was not clear to what extent Zelensky’s statement was a formal offer of compromise.

In other developments:
• Russian troops took staff and patients hostage at an intensive care hospital in the southern city of Mariupol, the local governor said.
• President Biden said he would attend a Nato summit in Brussels next week.
• Boris Johnson will fly to Saudi Arabia today for talks on buying more oil.

Asked if Zelensky’s words about not joining Nato were “a direct concession to Putin”, Antony Blinken, the US secretary of state, told CNN: “I don’t think that’s a concession. I think first of all it’s a reflection of reality that even before this aggression by Russia, Ukraine was not going to get into Nato tomorrow.”

Zelensky and his team have been upbeat about a ceasefire deal. Oleksiy Arestovich, an adviser, has said that the war will be over by May, when the Russians will run out of resources.

“I think that no later than in May, early May, we should have a peace agreement,” he said in a video posted on Ukrainian websites. “Maybe much earlier, we will see — I am talking about the latest possible dates.

“We are at a fork in the road now. There will either be a peace deal struck very quickly, within a week or two, with troop withdrawal and everything, or there will be an attempt to scrape together some, say, Syrians for a round two and, when we grind them too, an agreement by mid-April or late April.”

The Ukrainian side said that the talks included a broader agreement to lead to the withdrawal of Russian troops. At this stage, that would almost certainly require concessions because, despite the slow progress of the invasion, the Russians are still on the offensive.

Russian troops made further gains in the western suburbs of Kyiv, where Pierre Zakrzewski, an Irish cameraman working for Fox News, and Oleksandra Kuvshynova, a Ukrainian journalist, were confirmed to have been killed in shellfire on Monday.

Benjamin Hall, a British correspondent who was working with them, was severely injured and being treated for shrapnel injuries in a Kyiv hospital.

James Elder, a spokesman for Unicef who has spent the past two weeks in Ukraine, reported horrifying scenes faced by paediatricians trying to manage vast numbers of children arriving in hospitals across the country.

“A green sticker on a child means injured but we leave them,” he told a press conference. “A yellow sticker means [they] need attention; a red sticker means critical attention immediately. When the paediatricians are forced to put a black sticker on a child it means the child is alive but do not give attention because we don’t have the resources, and that child will die.”

Firefighters tackle a blaze caused by Russian shelling of a block of flats in Kyiv

VADIM GHIRDA/AP

The scale of the damage is revealed as smoke pours from the building

THOMAS PETER/REUTERS

In Mariupol, Pavlo Kyrylenko, the local governor, said he had received a message from an intensive care worker. “We can’t get out of the hospital,” it said. “They’re shooting a lot. We’re sitting in the cellar.”

He said that one of the hostages had told local authorities that the Russians had herded 400 people into the hospital, including staff and patients, who had been unable to leave since. An adviser to Zelensky said that 20,000 people were evacuated from Mariupol on Monday.

Sergei Orlov, Mariupol’s deputy mayor, said: “We received information that the Russian army captured our biggest hospital ... and they’re using our patients and doctors like hostages. We can confirm this information. We received information that there are 400 people there.”

Mairupol, a city of 400,000 people before the invasion, has been under almost constant bombardment for nearly two weeks and deprived of power and water supplies.

Last week a hospital was destroyed by a large bomb dropped by a Russian jet, killing at least four people and sparking widespread condemnation around the world. Large numbers of civilians being detained by Moscow’s troops — and potentially being used as human shields — marks a new tactic in the conflict.

To show their support for Zelensky, the prime ministers of Slovenia, Poland and the Czech Republic arrived for talks in Kyiv. “We must stop the tragedy as soon as possible,” Mateusz Morawiecki, the Polish prime minister, said.

Mevlut Cavusoglu, the Turkish foreign minister, will fly to Moscow and Kyiv today and tomorrow. Turkey is a Nato member and its troops have fought Russian-backed forces in Syria and Libya, but President Erdogan has forged a personal bond with Putin.

Nato is seeking to change its entire security posture in Europe in light of the invasion and Biden will meet other leaders in Brussels next week. Jens Stoltenberg, the Nato secretary-general, said: “We will address Russia’s invasion of Ukraine, our strong support for Ukraine, and further strengthening Nato’s deterrence and defence.”

Biden will also attend an EU meeting at which further sanctions on Russia will be discussed. The White House said that details of a trip to Poland were being finalised too.

The former prime minister Tony Blair has criticised as a “strange tactic” Nato’s insistence that it will not get involved in the conflict. “Suppose he uses chemical weapons or a tactical nuclear weapon, or tries to destroy Kyiv as he did Aleppo in Syria,” he said. “Is it sensible to tell him in advance that, whatever he does militarily, we will rule out any form of military response? Maybe that is our position and maybe that is the right position, but continually signalling it, and removing doubt in his mind, is a strange tactic.”