The Russian military alleged Thursday that its forces have managed to capture more of the outer neighbourhoods of Mariupol, in southeastern Ukraine, saying the operation to "liberate" the strategic port city is ongoing.

The claim came a day after a Russian airstrike destroyed a children’s hospital and maternity ward in Mariupol, where heavy fighting has been taking place in recent days.

Local authorities in the besieged city have accused Russian forces of waging a "medieval siege" against them.

-ABC News' Patrick Reevell

The top diplomats from Russia and Ukraine are meeting now in Antalya, Turkey.

Russian Foreign Minister Sergey Lavrov and Ukrainian Foreign Minister Dmytro Kuleba arrived in the southern Turkish resort on Thursday morning ahead of the meeting -- the highest level talks between their two countries since Russia invaded Ukraine on Feb. 24.

Both officials first met separately with their Turkish counterpart, Mevlut Cavusoglu, upon arrival. Cavusoglu is expected to attend their talks.

Lavrov and Kuleba are expected to talk for about 90 minutes. They will hold separate press conferences afterwards.

-ABC News' Engin Bas and Joe Simonetti

Russia’s foreign ministry has claimed that Ukraine put firing positions inside the children’s hospital and maternity ward in Mariupol, Ukraine, that was destroyed by shelling Wednesday.

There is currently no evidence to support the claim, made by Foreign Ministry spokeswoman Maria Zakharova during a daily briefing Wednesday. The comment appears to be an implicit acknowledgment that Russia deliberately targeted the hospital, as Ukrainian officials had claimed.

Independent investigations found that in Syria, Russia’s air force deliberately bombed hospitals in rebel-held areas as a tactic of war.

-ABC News' Patrick Reevell

The State Department spoke out against the Kremlin's allegations of U.S. chemical or biological weapons activity in Ukraine.

"Russia has a track record of accusing the West of the very crimes that Russia itself is perpetrating," State Department spokesperson Ned Price said in a statement Wednesday, calling the allegations of U.S. biological weapons labs and chemical weapons development in Ukraine "outright lies," "conspiracy theories," "disinformation" and "total nonsense."

"Russia is inventing false pretexts in an attempt to justify its own horrific actions in Ukraine," he continued. "The United States does not own or operate any chemical or biological laboratories in Ukraine, it is in full compliance with its obligations under the Chemical Weapons Convention and Biological Weapons Convention, and it does not develop or possess such weapons anywhere."

-ABC News' Conor Finnegan

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler