The head of the pro-Russian rebels in the self-proclaimed "People's Republic" of Donetsk in eastern Ukraine has called for "general mobilization".

"Today I signed a decree on general mobilization," said Denis Puschilin in a video message published on Saturday.

He called on citizens who were reservists to "come to the military enrollment offices."

In addition, the Ukrainian army and the pro-Russian rebels accused each other of serious violations of the ceasefire.

Puschilin asserted in the video that his soldiers had thwarted attacks planned by Ukraine.

The Ukrainian army continues its attacks.

"Together we will win for all of us the victory we desire and deserve," said the rebel leader.

"We will protect the Donbas and the entire Russian people."

In his speech, Pushilin urged civilians to flee to neighboring Russia.

First, "women, children and the elderly" should be brought to safety, said the separatist chief.

"A temporary departure will save you and your relatives' lives." Ukraine has repeatedly denied allegations that it intends to use force to retake areas controlled by pro-Russian rebels.

Biden's clearest statement to date

US President Joe Biden said on Friday he expects a Russian attack on the neighboring country in the "coming days".

In a televised White House address, Biden said he was "convinced" that Kremlin chief Vladimir Putin "has already made the decision to attack."

The Russian army plans to hold major maneuvers under Putin's supervision on Saturday.

According to Biden, the US government also assumes that the Russian armed forces would target the Ukrainian capital Kiev, among other things.

It was the clearest statement by the US President to date on Putin's alleged plans for an attack.

Previously, the US government had always stated that, in its estimation, the Russian President had not yet made a final decision on an attack.

A representative of the US Department of Defense has now said that between 40 and 50 percent of the Russian forces massed on the border with Ukraine have now "taken up an attack position".

Pentagon chief Lloyd Austin told ABC News that Putin had made preparations for a "successful invasion."

"I don't think this is a bluff," the defense secretary said.

But Biden doesn't see the door to diplomacy completely shut.

Moscow still has the choice between a "catastrophic and senseless war" and "diplomacy," he said.

Biden announced that US Secretary of State Antony Blinken would meet with Russia's chief diplomat Sergei Lavrov in Europe on Thursday.

Nato Secretary General Jens Stoltenberg also used drastic words to warn of a Russian invasion of Ukraine.

"There can be no doubt that we are now witnessing the greatest concentration of military forces in Europe since the end of the Cold War," Stoltenberg told ZDF.

A massive Russian troop deployment, which according to Western figures is now around 150,000 soldiers, has fueled fears of a Russian invasion of Ukraine for weeks.

Moscow denies any plans of attack and says it feels threatened by NATO.

222 violations of the ceasefire

Fears of a Russian invasion are also fueled by a sharp increase in violence in eastern Ukraine, where Ukrainian forces and pro-Russian rebels have been fighting each other for years.

Observers from the Organization for Security and Co-operation in Europe (OSCE) said on Saturday morning that they had noticed a "dramatic increase" in attacks along the front line in eastern Ukraine in the past few days.

In the area of ​​the Donetsk "People's Republic" proclaimed by the separatists, there were 222 violations of the ceasefire on Thursday, including 135 explosions, the OSCE said.

There were 189 such incidents there on Wednesday and 24 on Tuesday. According to the OSCE, there were 648 ceasefire violations in the Luhansk “People's Republic” on Thursday, after 402 on Wednesday and 129 on Tuesday.

Bombing near the village of Stanyzia-Luhanska continued on Friday, reporters from the AFP news agency reported.

On Thursday, a kindergarten was hit in the place controlled by the Ukrainian army.

The Ukrainian army and the pro-Russian separatists blamed each other for the incident.

The pro-Russian rebels called on civilians in the areas they controlled to “get to safety” in Russia.

Russian media also reported on Friday that an oil pipeline had exploded in the "People's Republic" of Luhansk.