A mosque in the southeastern Ukrainian port city of Mariupol, where 80 civilians were taking shelter, has been shelled by Russian forces, Ukraine's foreign ministry said on Saturday.

“The mosque of Sultan Suleiman the Magnificent and his wife Roxolana (Hurrem Sultan) in Mariupol was shelled by Russian invaders. More than 80 adults and children are hiding there from the shelling, including citizens of Turkey,” the ministry wrote on its Twitter account.

It did not specify when the shelling took place.

Contacted by AFP, the Turkish foreign ministry in Istanbul said it had “no information”.

However, the Ukrainian embassy in Ankara told AFP it had alerted Turkey's foreign ministry to the attack, without specifying when or whether it had received any response.

On Monday, the Turkish consulate in the southern port of Odessa had issued a tweet urging Turkish citizens to take shelter in the mosque “with a view to be being evacuated” to Turkey.

The consulate could not be reached by AFP on Saturday.

On Friday, the Ukrainian embassy in Turkey had forwarded to journalists a Facebook post by Mariupol's deputy mayor, Petro Andryushchenko, who said: “Right now, 86 Turkish citizens are being covered in the mosque territory. Thirty-four of them are kids.”

Friends and relatives of Turks living in Mariupol said they were anxious.

“My brother, Sahin Beytemur, has been living in Mariupol for eight years ... We haven't heard from him since last Saturday,” the 38-year-old shopkeeper's sister told AFP.

Others took to social media to try to locate the whereabouts of their loved ones.

“We have not heard from my aunt and cousin who have been living there for 11 days. We have no idea whether they are alive or not. Communication is completely lost we don't know what to do,” wrote one Twitter user, @brsyrdm11.

Turkey is a close ally of Ukraine but has refused to cut ties with Moscow and even tried to mediate between the two sides, hosting a first meeting of the Russian and Ukrainian foreign ministers on Thursday in Antalya.

'Humanitarian catastrophe'

Mariupol has been under siege and bombardment for more than a week and is encircled by Russian troops.

The situation in the strategic port city was “desperate”, where civilians have been desperately trying to flee, but were without water or heating, and running out of food, a top Doctors Without Borders executive said on Friday.

Ukrainian Foreign Minister Dmytro Kuleba tweeted on Friday: “Besieged Mariupol is now the worst humanitarian catastrophe on the planet. 1,582 dead civilians in 12 days.”

Three people, including a child, were killed when a children's hospital in the city was attacked on Wednesday, sparking international outrage.

Against this backdrop, a new attempt is being made to open up a humanitarian corridor to allow civilians to evacuate the city towards Zaporizhzhia, around 200 kilometres to the north east, said Ukraine's Deputy Prime Minister Iryna Vereshchuk.

For days, Ukrainians have claimed that the Russian military has been pounding the evacuation route, preventing people from leaving.

As on previous days, humanitarian corridors were also to be opened again around Kyiv.

“I very much hope that the day will go well, that the planned routes will be open and that Russia will meet its obligations regarding the observance of the ceasefire,” Vereshchuk said in a video uploaded to the website of the Ukrainian presidency.

As the Russian army continues to advance and besiege Kyiv, strikes hit the town of Vasylkiv on Saturday morning, about 40 kilometres south of the capital.

Eight Russian rockets hit the local airport around 7:00 am local time, which was “completely destroyed”, said the mayor Natalia Balassinovitch, on her Facebook account.

An oil depot was also hit and caught fire, she said.

Ukrainian president says Russia sending new troops after heavy losses

Meanwhile, Ukrainian President Volodymyr Zelensky said Russia was sending new forces to Ukraine after suffering what he said were its biggest losses in decades.

Zelensky also said he had spoken to German Chancellor Olaf Scholz and French President Emmanuel Macron about pressuring Russia to release the mayor of the city of Melitopol, who Ukraine says was kidnapped on Friday by Russian forces.

In a televised address, Zelensky urged Russia to uphold an agreed ceasefire to allow evacuations to proceed from the besieged port city of Mariupol, after blaming Moscow for the failure of previous attempts.