THE US EMBASSY in Kyiv has warned of a “potential significant air attack” and shuttered its doors, following Russia’s vow to respond after Ukraine fired longer-range US missiles at its territory for the first time.

“The US Embassy in Kyiv has received specific information of a potential significant air attack on November 20,” it said in a message on its website.

“Out of an abundance of caution, the Embassy will be closed, and Embassy employees are being instructed to shelter in place. The U.S. Embassy recommends U.S. citizens be prepared to immediately shelter in the event an air alert is announced.”

Ukraine this week fired US-supplied long-range missiles into Russian territory, the first such attack since the United States gave Kyiv approval to do so over the weekend. 

Russia’s Foreign Minister Sergei Lavrov criticised Washington’s decision to let Ukraine to use the missiles, which have a range of up to 300 kilometres, and said it marks a “new phase of the Western war against Russia”.

Its defence ministry said Ukraine fired six US-made ATACMS missiles yesterday at a military facility in Russia’s Bryansk region, adding that air defences shot down five of them and damaged one more.

US President Joe Biden authorised Ukraine to use long-range American missiles against military targets inside Russia on Sunday. 

The decision was a major US policy shift and came as Biden prepares to leave the White House in January.

Lavrov said the missiles could not have been fired without US technical assistance and said the strikes showed the West and Kyiv want “escalation”.

Ukrainian Foreign Minister Andriy Sybiga has urged Ukraine’s Western allies to remain “clear-eyed and not give into fear” in the face what he termed Russian “saber-rattling” over its nuclear weapons.

Ukrainian President Volodymyr Zelenskyy and many of his Western supporters had been pressing Biden for months to allow Ukraine to strike military targets inside Russia with Western-supplied missiles, saying the US ban had made it impossible for Ukraine to try to stop Russian attacks on its cities and electrical grids. 

But Russia had indicated that any such move would be met with retaliation against Nato. 

Russian President Vladimir Putin yesterday signed a decree broadening the scope of when Moscow can use nuclear weapons.

Moscow has said the use of Western weapons against its internationally recognised territory would make the US a direct participant in the conflict.

The new doctrine outlines that Russia will consider using nuclear weapons against a non-nuclear state if they are supported by nuclear powers.

White House officials were not surprised by Putin’s decision, and the US had seen no change to Russia’s nuclear posture, according to a US National Security Council official.

As a result, the Biden administration had “not seen any reason to adjust our own nuclear posture or doctrine in response to Russia’s statements today”, the official added. Still, the official said, the White House viewed it as “irresponsible rhetoric”.