US says war appears imminent after shelling on Ukraine front line

US President Joe Biden said that there was every indication that Russia was planning to invade Ukraine after Ukrainian forces and pro-Moscow rebels traded fire.

US President Joe Biden said that there was now every indication Russia was planning to invade Ukraine, including signs Moscow was carrying out a false flag operation to justify it, after Ukrainian forces and pro-Moscow rebels traded fire.

Moscow, for its part, ejected the number two official from the US embassy and released a strongly worded letter accusing Washington of ignoring its security demands. It threatened unspecified "military-technical measures".

Early morning exchanges of fire between Ukraine and pro-Russian separatists raised alarm, with Western officials who have long warned that Moscow could try to create a pretext for an invasion saying they believed such a scenario was now unfolding.

"We have reason to believe they are engaged in a false flag operation to have an excuse to go in. Every indication we have is they're prepared to go into Ukraine and attack Ukraine," Biden told reporters as he departed the White House.

Biden ordered Secretary of State Antony Blinken to change his travel plans at the last minute to speak at a United Nations Security Council meeting on Ukraine.

"The evidence on the ground is that Russia is moving toward an imminent invasion. This is a crucial moment," US Ambassador to the United Nations, Linda Thomas-Greenfield, told reporters.

Russia denies planning to invade its neighbour and said this week it was pulling back some of the more than 100,000 troops it has massed near the frontier. Washington says Russia is not withdrawing, but in fact sending more forces.