The US and its NATO allies have so far sent 17,000 anti-tank missiles and 2,000 stinger anti-aircraft missiles to support Ukraine in its war against Russia, according to US media reports.

Deputy Foreign Minister Sergei Ryabkov said today that Russia had warned the US that "pumping weapons from a number of countries isn't just a dangerous move, it's an action that makes those convoys legitimate targets".

He also denounced the US sanctions against Moscow as an "unprecedented attempt to deal a serious blow to various sectors of the Russian economy".

Mr Ryabkov added Moscow will act in a measured way to avoid hurting itself.

The deputy foreign minister also said Russia has no intention to expel Western media and businesses amid the soaring tensions with the West, adding that "we aren't going to escalate the situation".

Key developments:

• Vladimir Putin's forces continued to launch airstrikes in Kyiv, Kharkiv and Mariupol on Friday

• Russia also used high-precision, long-range weapons to put military airfields in Lutsk and Ivano-Frankivsk "out of action"

• The mayor of a Ukrainian city has been abducted by Russian forces, President Volodymyr Zelenskyy says

• Thousands of civilians and soldiers on both sides are believed to have been killed in the invasion so far

• Putin has claimed there have been "certain positive developments" in talks between Ukraine and Russia

• 7,144 people were evacuated from four Ukrainian cities on Friday, Mr Zelenskyy says

Vasylkiv airbase struck by Russian rockets

New satellite images show homes on fire as Russian troops advance closer to Kyiv, with long lines of cars trying to flee the Ukrainian capital.

The UK's Ministry of Defence has also warned that "staunch resistance" from Ukraine means Russian tactical aircraft are relying on unguided "dumb" munitions.

"Such weapons are relatively inaccurate and indiscriminate and their use significantly increases the likelihood of civilian casualties," a defence intelligence update released on Friday night said.

Fighting has raged northwest of Kyiv this morning, with the bulk of Russian ground forces 16 miles (25km) from the centre of the Ukrainian capital, while several other cities were encircled and under heavy shelling, the defence ministry added.

The mayor of Vasylkiv in the Kyiv region has said Russian rockets have destroyed a Ukrainian airbase near the town.

The rocket attacks also hit an ammunition depot, Mayor Natalia Balasynovych told the Interfax Ukraine news agency.

Analysts divided on what images mean

The satellite images from Maxar appear to suggest that Russian military units are "actively firing artillery towards residential areas" - and in one photograph, a bright muzzle flash can be seen from an artillery gun.

Widespread damage and impact craters have been seen in Moschun, a town northwest of Kyiv, and fires are continuing to burn at Hostomel Airport, which is also known as Antonov Airport.

A 40-mile (64km) line of tanks and other vehicles had amassed outside Kyiv early last week - but progress by Russian troops appeared to have stalled amid reports of food and fuel shortages, muddy roads, and attacks by Ukrainian troops using anti-tank missiles.

On Thursday, satellite images appeared to show that this convoy had largely dispersed and redeployed - fanning out into surrounding towns and forests.

Mathieu Boulegue, a researcher at the Chatham House think tank, believes the redeployment means the battle for Kyiv could be hours or days away - and it could be a drawn-out siege.

"This is going to be a very long battle of attrition. This is going to be an atrociously casualty-heavy battle and a siege, the likes of which we have rarely seen in modern history," he said.

The UK's Ministry of Defence has said Russia is currently attempting to "reset and reposture" its troops - and Nick Reynolds, a warfare analyst at the Royal United Services Institute, said: "It's ugly already, but it's going to get worse."

However, a senior US defence official believes that elements of this convoy have broken away to ensure vehicles are better hidden and protected.

They added that the convoy has not made any substantial progress towards Kyiv, and the moves seen over recent days were not thought to be part of a tactical effort to advance on the capital.

Despite this, other forces northeast of Kyiv have moved closer - and they are now 12 to 19 miles (20km to 30km) east of the city centre.

Mayor of Ukrainian city 'abducted'

The developments come as Ukrainian President Volodmyr Zelenskyy said the mayor of the city of Melitopol has been kidnapped by Russian forces.

Mr Zelenskyy equated the kidnapping to the actions of "IS terrorists", and said Russian forces "have transitioned into a new stage of terror".

Ukraine's parliament has claimed Ivan Fedorov was abducted by a group of 10 armed men who put a plastic bag over his head.

A growing humanitarian crisis

The number of people who have fled Ukraine during the war has now passed 2.5 million.

Iryna Vereshchuk, deputy prime minister of Ukraine, has said several humanitarian corridors, including one from the besieged southern city of Mariupol to Zaporizhzhia, could open on Saturday.

At least 1,582 civilians have been killed as a result of shelling and a 12-day blockade on Mariupol, the city's council said on Friday.

Efforts to provide safe passage for residents of Mariupol have repeatedly failed this week.

Ms Vereshchuk said she hopes Russia will observe a ceasefire to allow the latest effort to take place.

The deputy prime minister also said Ukraine plans to evacuate residents of several towns and villages in the regions of Kyiv and Sumy and some other areas where there is ongoing combat.

Temperatures have fallen below freezing across most of the country - and lows of -13C have been forecast in the city of Kharkiv, which has faced heavy bombardment. Hundreds of apartment buildings there have also lost heat.

Speaking from Kyiv, President Zelenskyy said: "It's impossible to say how many days we will still need to free our land, but it is possible to say that we will do it."

A Western official speaking anonymously to the AP news agency said the fact that negotiations are taking place so early in the fighting "might speak to Russian concerns" about the progress of the war.

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