The US has claimed Russia is planning to stage a fake Ukrainian attack that it would use to justify an invasion.

It alleged Moscow was likely to release a graphic video showing the attack on Russian territory or against Russian-speaking people in eastern Ukraine.

Russia denied it was planning to fabricate an attack, and the US did not provide evidence to support the claim.

The build-up of tens of thousands of Russian troops on Ukraine's borders has escalated fears of an invasion.

Moscow says they are there for military drills, but Ukraine and its Western allies remain concerned that Russia is planning to launch an assault.

"We do have information that the Russians are likely to want to fabricate a pretext for an invasion," Pentagon spokesman John Kirby told reporters on Thursday.

"As part of this fake attack, we believe that Russia would produce a very graphic propaganda video, which would include corpses and actors that would be depicting mourners and images of destroyed locations," he said.

But senior US officials said the video was just one of several ideas Russia has to provide a pretext to invade its neighbour.

They added that the alleged plan was being revealed in an effort to dissuade Russia from invading.

Kremlin spokesman Dmitry Peskov responded to the reports later on Thursday.

"This is not the first promise of its kind [to release details about Russian provocation]," he said. "Something similar was also said before, but nothing came of it."

Russia has repeatedly denied that it is planning an attack.

News of the alleged plot came a day after the US said it was sending more troops to eastern Europe to support allies in the Nato defensive alliance.

Russia said the move was "destructive" and showed that its concerns about Nato's eastward expansion were justified.

Also on Thursday, Nato expressed concerns that Russia was likely to deploy up to 30,000 troops - including special forces, fighter jets and short-range ballistic missiles - in Belarus, Ukraine's northern neighbour.

"This is the biggest Russian deployment there since the Cold War," Nato Secretary General Jens Stoltenberg said.

Rivalry between Russia and the US, which still possess the world's biggest nuclear arsenals, dates back to the Cold War. Ukraine was then a crucial part of the communist Soviet Union.

Russian President Vladimir Putin is currently in the Chinese capital, Beijing, for the Winter Olympics, and on Friday met his Chinese counterpart, Xi Jinping, for their first face-to-face meeting since June 2019, because of the pandemic.

The two nations have a close relationship - President Xi has previously praised Mr Putin as his "best friend", and it is widely expected that Russia will be looking for diplomatic support from China as tensions build with Ukraine and the West.

Meanwhile, French President Emmanuel Macron will travel to Russia and Ukraine next week to try and de-escalate the tensions. He will meet Mr Putin in the Russian capital, Moscow, on Monday, then Ukraine's President Volodymyr Zelensky the next day.

UK Prime Minister Boris Johnson was in Ukraine earlier this week in an effort to "avoid further bloodshed".