Separatists in Ukraine asked for Russian help to repel "aggression" on Wednesday and Kyiv announced compulsory military service and a state of emergency as the West slapped more sanctions on Moscow in a bid to stop an all-out invasion.

In one of the worst post-Cold War security crises in Europe for decades, convoys of military equipment, including nine tanks, moved towards the eastern Ukrainian area of Donetsk from the direction of the Russian border, a Reuters witness reported.

Shelling has intensified in the east, where Russian President Vladimir Putin has recognised two separatist regions as independent and ordered the deployment of what he called peacekeepers, a move the West calls the start of an invasion.

But there was still no clear indication of whether Putin will launch a massed assault on Ukraine with the tens of thousands of troops he has gathered on its borders. Moscow has long denied that it has plans to invade.

The leaders of the two breakaway areas want Putin to intervene.

"I am asking for help to repel the Ukrainian regime's military aggression against the population of the Donetsk People's Republic," said Denis Pushilin who heads the area Moscow recognised as independent, according to TASS news agency.

The White House rejected the comments as another Russian false flag operation, a fake crisis manufactured to justify greater Russian military intervention in Ukraine.

"This is an example of it," White House press secretary Jen Psaki told reporters. "That is suggesting that they feel under threat. By whom? The Ukrainians that the Russians are threatening to attack?"

Kyiv warned the move was an escalation of Russia's military pressure and sought an urgent meeting of the U.N. Security Council. Ukrainian President Volodymyr Zelenskiy said Moscow had approved an offensive and not replied to an invitation for talks.

"Today I initiated a telephone conversation with the President of the Russian Federation. The result was silence," he said.

U.N. chief Antonio Guterres has dismissed claims of a genocide in eastern Ukraine. Under international law, genocide is an intent to destroy, in whole or in part, a national, ethnical, racial or religious group.

A total of 80% of the soldiers assembled are in a position to launch a full-scale invasion on Ukraine, a senior U.S. defence official said.

Satellite imagery taken on Wednesday showed new deployments in western Russia, many of them within 10 miles (16 km) of the border with Ukraine and less than 50 miles from the Ukrainian city of Kharkiv, a U.S. company Maxar said.

The images showed field deployment, military convoys, artillery and armoured personnel carriers with support equipment and troops. The images could not be independently verified by Reuters.

A 30-day state of emergency in Ukraine restricting the freedom of movement of conscripted reservists, curbing the media and imposing personal document checks, according to a draft text, begins on Thursday.

The Ukrainian government has also announced compulsory military service for all men of fighting age.

SANCTIONS

While the West has held off the most stringent sanctions measures it could impose, the United States stepped up the pressure by imposing sanctions on the firm building the Nord Stream 2 gas pipeline and its corporate officers.

"We will not hesitate to take further steps if Russia continues to escalate," said U.S. President Joe Biden.

The White House said the sanctions do not affect former German chancellor Gerhard Schroeder, who has headed the shareholders committee of Nord Stream since 2005.

Germany on Tuesday froze approvals for the pipeline, which has been built but was not yet in operation.

The rouble plunged more than 3% as the European Union blacklisted Russian lawmakers, freezing their assets and banning travel. Wall Street slipped on news of security measures taken by Ukraine's government.

Ukrainian government and state websites, which have experienced outages in recent weeks blamed by Kyiv on cyber attacks, were again offline on Wednesday. Ukraine's parliament, cabinet and foreign ministry websites were affected.

Moscow has described warnings of an invasion as anti-Russian hysteria. On Wednesday, it took down flags from its embassy in Kyiv, having ordered its diplomats to evacuate for safety reasons.

Ukraine's military said one soldier had been killed and six wounded in increased shelling by pro-Russian separatists using heavy artillery, mortar bombs and Grad rocket systems in the two breakaway areas in the last 24 hours.

For months, Russia has presented the crisis mainly as a dispute with the West, demanding security guarantees, including a promise never to allow Ukraine to join NATO.

But the recognition of the separatist regions was accompanied by much stronger language against Ukraine, which Putin called an artificial construct wrongly carved out of Russia by its enemies.

"In the case of Putin, this is not a struggle for money or power: It's about pride, which means the mind is switched off," said Lilia, 72, a pensioner in a Kyiv suburb. "He can't stop, and he can't be stopped."