Ukraine said on Thursday Moscow had refused to guarantee humanitarian access to rescue hundreds of thousands of civilians trapped under bombardment, as the opposing sides yielded nothing at the highest level talks since the Russian invasion began.

Russia's war in Ukraine entered the third week with none of its stated objectives reached, despite thousands of people killed, more than two million made refugees and thousands cowering in besieged cities under relentless bombardment.

Ukraine's Foreign Minister Dmytro Kuleba met Russia's Sergei Lavrov in Turkey, but said he had secured no promise from him to halt firing so aid could reach civilians, including Kyiv's main humanitarian priority - evacuating hundreds of thousands of people trapped in the besieged port of Mariupol.

"I made a simple proposal to Minister Lavrov: I can call my Ukrainian ministers, authorities, president now and give you 100% assurances on security guarantees for humanitarian corridors," he said.

"I asked him 'can you do the same?' and he did not respond."

Holding his own simultaneous news conference in a separate room, Lavrov showed no sign of making any concessions, repeating Russian demands that Ukraine be disarmed and accept neutral status. He said Kyiv appeared to want meetings for the sake of meetings and that a ceasefire was not meant to be on the agenda at the Turkey talks.

Russia calls its actions a special military operation to disarm its neighbour and dislodge leaders it calls neo-Nazis. Kyiv and its Western allies say this is a baseless pretext to invade a country of 44 million people.

Aid agencies say humanitarian aid is most urgently needed in Mariupol, where 400,000 people have been trapped for more than a week with no food, water or power. The city council said the port had come under fresh air strikes on Thursday morning, a day after Moscow bombed what Ukraine called a functioning maternity hospital there.

Lavrov said the building was no longer used as a hospital and had been occupied by Ukrainian forces. The Kremlin did not initially repeat that denial and said the incident was being investigated.

"What kind of country is this, the Russian Federation, which is afraid of hospitals, is afraid of maternity hospitals, and destroys them?" President Volodymyr Zelensky said in a televised address late on Wednesday, after posting footage of the wreckage.

Ukraine said a convoy trying to reach the city had again been turned back by Russian fire on Thursday, and accused Moscow of deliberately blocking aid. Daily attempts at a local humanitarian ceasefire have failed since Saturday.

Lavrov repeatedly lashed out at the West, accusing Western countries of inflaming the situation by arming Ukraine. Asked if the conflict could lead to nuclear war, he said: "I don't want to believe, and I do not believe, that a nuclear war could start."

LITTLE PROGRESS

Moscow's stated objectives of crushing Ukraine's military and removing its leaders have remained out of reach, with Zelensky unshaken and Western military aid pouring across the Polish and Romanian borders.

Russian forces have advanced in the south but have yet to capture a single city in the north or east. Western countries have said they believe a planned lightning strike on Kyiv failed in the early days of the war, and Moscow has instead turned to tactics that involve far more destructive assaults.

The UK Defence Ministry said on Thursday that a large Russian column northwest of Kyiv had made little progress in over a week and was suffering continued losses. It added that as casualties mount, Russian President Vladimir Putin would have to draw from across the armed forces to replace the losses.

Western-led sanctions designed to cut the Russian economy and government from international financial markets have bitten hard, with the rouble plunging and ordinary Russians rushing to hoard cash.

Britain added several Russian businessmen to its blacklist on Thursday, including Roman Abramovich, owner of Chelsea soccer team. The sanctions would block an attempt to sell the club, but a special license would let it keep playing.

'HOSPITAL BOMBED'

Ukrainian officials said Russian aircraft bombed the children's hospital on Wednesday, injuring pregnant women and burying patients in rubble despite a ceasefire deal to allow people to flee Mariupol. The regional governor said 17 people were wounded.

The attack underscored U.S. warnings that the biggest assault on a European state since 1945 could become increasingly attritional after Russia's early setbacks.

The White House condemned the bombing as a "barbaric use of military force to go after innocent civilians".

The U.N. Human Rights body said it was trying to verify the number of casualties. The incident "adds to our deep concerns about indiscriminate use of weapons in populated areas," it added through a spokesperson.

Russia has repeatedly pledged since Saturday to halt firing so at least some trapped civilians could escape Mariupol. Both sides have blamed the other for the failure of the evacuations.

Half of the more than 2 million total refugees from Ukraine are children. The International Committee of the Red Cross said houses had been destroyed all across Ukraine. "Hundreds of thousands of people have no food, no water, no heat, no electricity and no medical care," it said.

Ukraine's gas transit company said Russian forces were occupying gas pumping stations threatening shipments to Europe. So far gas is still flowing normally.

Russia has been hit by Western sanctions and the withdrawals of foreign firms, the latest including Nestle, cigarette maker Philip Morris and Sony.

Rio Tinto on Thursday became the first major mining company to announce it was cutting all ties with Russian businesses.

The U.S. House of Representatives on Wednesday voted to rush $13.6 billion in aid to Ukraine, sending the legislation to the Senate.