Ukraine sees no point closing its airspace amid the tensions with Moscow, a senior Ukrainian official said on Sunday, after the United States warned that Russia could invade the eastern European nation at any time.

Dutch carrier KLM said it would stop flying to Ukraine and Germany's Lufthansa said it was considering suspending flights.

Ukraine's SkyUp said on Sunday it had to divert one flight after the owner of the leased aircraft barred it from entering Ukrainian airspace.

“The most important point is that Ukraine itself sees no point in closing the sky. This is nonsense. And, in my opinion, it somewhat resembles a kind of partial blockade,” said Mykhailo Podolyak, an adviser to Ukrainian president's chief of staff.

“If particular air carriers decide to reconfigure the flight schedule, this certainly has nothing to do with the decisions or policies of our state,” he told Reuters.

The United States, its Western allies and other nations have been scaling back or evacuating embassy staff and have advised their citizens not to travel to Ukraine amid the standoff.

Also read: Russia could invade Ukraine 'any time', including during Olympics: Blinken

Washington says the Russian military, which has more than 100,000 troops massed near Ukraine, could invade at any moment.

Moscow denies having any such plan and has described such warnings as “hysteria”.

At Kyiv's Borispil Airport, the largest in Ukraine, there was little sign on Saturday of an exodus. Oksana Yurchenko was travelling back to Australia with her child.

“We were visiting our family here in Ukraine. We were planning to stay a bit longer but this situation is a bit scary,” the chef and a beauty salon owner said.

Australia has advised its citizens to leave Ukraine and said on Sunday it was evacuating its embassy.

Ricky, a Scotsman who lives in Ukraine, said he saw no sign of public anxiety on the streets. “I do not see anyone in fear in Ukraine, everyone is just getting on with their life,” he said at the airport as he waited for a flight to go on holiday.

Ukraine's SkyUp said in a statement that one of its planes, carrying 175 passengers from Portugal, had to land in Moldova on Saturday instead of continuing to Ukraine after the Ireland-based owner of the leased aircraft prevented the aircraft from entering Ukrainian airspace.

It did not give further details.

KLM, part of Air France, said it would stop flying to Ukraine immediately, news agency ANP reported on Saturday, while Lufthansa said it was considering suspending air traffic to Ukraine but had yet to decide.

Two third of the 298 passengers killed when Malaysia Airlines MH17 was shot down over eastern Ukraine in 2014, as it flew from Amsterdam to Kuala Lumpur, were Dutch citizens.