Ukraine's strategic port city of Mariupol is under a "blockade" by Russian forces after days of "ruthless" attacks, its mayor said on Saturday, calling for the establishment of a humanitarian corridor. 

Located on the Sea of Azov, the city of 450,000 people has been bombarded by shellings and cut off without water or electricity in the depths of winter.

"For now, we are looking for solutions to humanitarian problems and all possible ways to get Mariupol out of the blockade," said Vadim Boychenko in a message posted to the mayor's Telegram account.

"Our priority is the establishment of a ceasefire so that we can restore vital infrastructure and set up a humanitarian corridor to bring food and medicine into the city," he added.

Capturing Mariupol would give Moscow's invasion a strategic advantage, connecting it to the Russian forces coming from annexed Crimea -- which have already taken the key ports of Berdiansk and Kherson -- as well as to the troops in the Donbas.

Earlier this week, the Mariupol mayor had accused Russian troops of destroying bridges and trains to prevent residents from leaving. 

"For five days, our hometown, our family of half a million people, has been under ruthless attack," he wrote on Saturday, while calling for continued resistance.

Nato under fire

Ukrainian President Volodymyr Zelensky lashed NATO on Friday for ruling out a no-fly zone over his country saying the Western military alliance knew further Russian aggression was likely.

Earlier Friday, NATO rejected Ukraine's request to impose a no-fly zone to halt Russia's bombing, but Western allies did warn President Vladimir Putin of fresh sanctions if he does not stop the war.

"Knowing that new strikes and casualties are inevitable, NATO deliberately decided not to close the sky over Ukraine," Zelensky said in a video published by the presidency.

"We believe that the NATO countries themselves have created a narrative that the closing of the skies over Ukraine would provoke direct Russian aggression against NATO."

NATO chief Jens Stoltenberg had said the alliance would not intervene in the conflict over fears of a direct clash with Moscow that could spiral into a wider conflict.

"The only way to implement a no-fly zone is to send NATO fighter planes into Ukraine's airspace, and then impose that no-fly zone by shooting down Russian planes," Stoltenberg said after the urgent meeting.

"If we did that, we'll end up with something that could end in a full-fledged war in Europe, involving many more countries and causing much more human suffering."

But Zelensky insisted that the NATO gathering was a "weak summit, a confused summit".

"All the people who die starting today will also die because of you. Because of your weakness, because of your disconnection," he said.

"Today the leadership of the alliance gave the green light for further bombing of Ukrainian cities and villages, refusing to make a no-fly zone."

Italy seizes Russian oligarch's yacht

Italy said Friday that it seized the yacht of a Russian oligarch who is seen as close to President Vladimir Putin and is subject to EU sanctions.

"Italy's police has just seized 'Lady M Yacht', a 65 million euros ($70 million) vessel belonging to Alexey Alexandrovits Mordaschov located in Imperia (Liguria) -- in compliance with the recent EU sanctions," Ferdinando Giugliano, a media adviser to Italy's prime minister, said in a tweet.

Steel magnate Mordashov owns Severstal group and is among the ultra-wealthy, influential Russians blacklisted by Brussels for their perceived closeness to the Kremlin.

Since Russia's invasion of Ukraine began on February 24, the EU has moved to freeze the assets of connected oligarchs and bar them from entering the bloc.

Mordashov used a statement issued Monday to distance himself from Putin's war in Ukraine.

"I have absolutely nothing to do with the current geopolitical tensions and I don't understand why the EU has imposed sanctions on me," he said.

Italian media have reported that another yacht, the Lena owned by Gennady Timchenko, the billionaire co-founder of commodities trader Gunvor, has been seized in Sanremo.

The first yacht seized as a result of EU sanctions was the Amore Vero, snatched Thursday in the French port of La Ciotat. 

The mega-yacht belongs to a company linked to the head of Russian oil giant Rosneft. 

Yachts, symbols of the massive wealth accrued by Russia's elite, are among their overseas assets being targeted by Western sanctions. 

The EU sanctions target more than 500 Russian individuals or entities whose assets are to be traced and frozen.

Day nine of Russia's invasion

On the ninth day of Russia's invasion of Ukraine Friday, Russian forces pressed an advance into the country but are still facing resistance in their bid to seize major cities.

The capital Kyiv remains under Ukrainian control as does Kharkiv in the east despite heavy Russian bombardment. Russian forces have seized Kherson in the south and have encircled urban centres in the region.

Here is a summary of the situation on the ground, based on statements from the sides, Western defence and intelligence sources and international organisations.

- The east
Kharkiv remains in Ukrainian hands despite intense bombardments, according to Western sources.

Russian forces are also pressing an offensive through the Russian-backed separatist Donetsk and Lugansk regions although how far they have penetrated remains unclear.

- Kyiv and the north
Kyiv remains under Ukrainian control, despite heavy bombardments, although Western observers have pointed to a major Russian column of hundreds of vehicle outside the city stationed around the Hostomel airfield. 

There has been heavy fighting in the vicinity of Hostomel but the column has made little progress in recent days.

Regional authorities said 47 people were killed in a Russian air strike in the northern city of Chernigiv.

Zhytomyr west of Kyiv has also come under heavy fire.

- The south
Ukraine this week acknowledged that Russia had taken control of the southern city of Kherson, the first urban centre that Moscow has captured.

A major fight is ongoing for the city of Mariupol, still under Ukrainian control, while Mykolayiv just west of Kherson is surrounded.

In Zaporizhzhia, Europe's largest atomic power plant was attacked and seized by invading Russian forces in a move that sparked international outrage.

Odessa remains in Ukrainian control and for now spared of fighting although there are fears of a possible amphibious assault on the city with Russian warships lurking off the Black Sea coast.

- The west
The west of Ukrainian remains largely spared from the fighting. The main western city of Lviv has become a hub for foreign diplomatic missions, journalists and Ukrainians seeking safety or seeking to leave the country.

- Casualties
Russia said Wednesday that 498 Russian troops had been killed in Ukraine, its first announced death toll.

Ukraine and Western sources claim that the real toll is far higher. Ukraine says over 9,000 Russian soldiers have been killed.

The UN said Wednesday that it had recorded nearly 230 civilian deaths in Ukraine, including 15 children, warning that the true toll was likely far higher.

- Refugees
Over 1.2 million refugees have fled Ukraine in the week since Russia's invasion, around half of them into Poland, according to the UN refugee agency.