Governments urge citizens to leave Ukraine immediately as war fears grow

Russia began removing diplomatic staff from Kiev on Saturday

Ukrainian soldiers stationed in Verkhnotoretske, amid concerns about a possible Russian invasion of the country. Getty

Tensions over a possible Russian invasion of Ukraine were mounting on Sunday as Australia and Israel followed the US in urging citizens to leave the country immediately, in addition to moving diplomatic staff.

Israel took the further step on Sunday of chartering commercial planes to fly out about 4,500 of its citizens in Ukraine.

On Thursday, US President Joe Biden called Russian leader Vladimir Putin to warn him that a further incursion into Ukraine (Russia annexed Crimea in 2014 and backed separatists in the east of the country) would lead to a “severe” response.

Following warnings from US officials that an invasion could occur at any time, Secretary of State Antony Blinken said on Saturday that diplomatic staff were being withdrawn.

"We ordered the departure of most of the Americans still at the US embassy in Kiev. The risk of Russian military action is high enough and the threat is imminent enough that this is the prudent thing to do," Mr Blinken told a news conference in Honolulu.

The US State Department said it appeared increasingly likely that the situation was headed towards "some kind of active conflict."

Australia's embassy staff in Kiev were also moved to a temporary office in Lviv, a city in western Ukraine, around 70 kilometres from the border with Poland, Foreign Minister Marise Payne said.

"We continue to advise Australians to leave Ukraine immediately by commercial means," Ms Payne said.

Australian Prime Minister Scott Morrison said that the situation "is reaching a very dangerous stage" and added that "the autocratic unilateral actions of Russia to be threatening and bullying Ukraine is something that is completely and utterly unacceptable."

Nato has been moving forces to countries bordering Ukraine in recent weeks amid a build-up of Russian troops on Ukraine's northern and eastern borders.

The Russian force is thought to have about 130,000 troops and support personnel, backed by field hospitals and engineering equipment that would be required for a large-scale attack.

Amid the build-up of forces, the US denied that it had carried out military operations in Russian territorial waters on Saturday, after Moscow said a Russian naval vessel chased away a US submarine in Russian waters in the Pacific.

Interfax news agency cited the Russian Defence Ministry as saying a Russian naval vessel chased away a US submarine in Russian waters in the Pacific after the submarine ignored the ship's orders to surface.

"There is no truth to the Russian claims of our operations in their territorial waters," said Capt Kyle Raines, a US military spokesman.

"I will not comment on the precise location of our submarines but we do fly, sail, and operate safely in international waters," he said.

It is common for the US to monitor military activity being carried out by other countries without having to enter their territorial waters.

The crew of the Marshal Shaposhnikov frigate used "corresponding means" to make the submarine leave Russian waters, the Russian Defence Ministry was quoted as saying.

It said it had called in the US defence attache over the incident.

The submarine was spotted near the Kuril Islands early on Saturday as Russia was conducting naval exercises with its Pacific Fleet and it was ordered to surface immediately, the Russian ministry was quoted as saying.

On Saturday, Russia also removed diplomatic staff from Kiev.