Ukraine crisis: 'Russia wants to start World War Three', Prime Minister warns after pro-Russians accused of shooting down helicopter

Ukrainian PM warns military conflict could spread to the rest of Europe

Tensions are continuing to mount in Ukraine after Kiev officials claimed pro-Russian snipers shot at an Ukrainian military helicopter, causing it to explode over a military base.

The unverified reports said the helicopter was hit by a rocket-propelled grenade in the eastern town of Kramatorsk, just hours after the Ukrainian Prime Minster Arseny Yatsenyuk accused Russia of wanting to start World War Three by occupying Ukraine both “militarily and politically”.

“According to a preliminary assessment, the explosion was the result of fire from a rocket-propelled grenade launcher,” the Ukrainian defence ministry said in a statement. The pilot was wounded in the incident, according to reports.

Earlier, Mr Yatsenyuk said an occupation would create a conflict that could spread to the rest of Europe.

“Attempts at military conflict in Ukraine will lead to a military conflict in Europe,” Mr Yatsenyuk told the interim cabinet in remarks broadcast live. “The world has not yet forgotten World War Two, but Russia already wants to start World War Three.”

His comments came as Ukraine’s defence minister Mykhailo Koval said a column of Russian troops conducting exercises close to the Ukrainian frontier came within one kilometre of the border, but did not cross. Mr Koval cautioned: “Ukraine's armed forces are ready to repel any aggression.”

Meanwhile, the Russian Foreign Minister Sergei Lavrov warned today Kiev's interim government would face justice for a ”bloody crime“ in eastern Ukraine and accused Washington of distorting an agreement designed to defuse the crisis.

He also criticised the US Secretary of State John Kerry for an ”unacceptable, accusatory tone“ after Mr Kerry suggested on Thursday that Washington was close to imposing more sanctions on Russia over the Ukrainian crisis.

Mr Kerry accused Moscow of attempting to ”destabilise“ Ukraine in a forceful statement.

”Russian President Vladimir Putin and Russia face a choice,“ he said during an appearance at the State Department on Thursday.

”Following today's threatening movement of Russian troops right up to Ukraine's border, let me be clear: If Russia continues in this direction, it will not just be a grave mistake, it will be an expensive mistake.

“If Russia chooses the path of de-escalation ... all of us will welcome it. But if Russia does not, the world will make sure that the costs for Russia will only grow.”

The Russian army began new military manoeuvres close to the Ukrainian border on Thursday, hours after President Vladimir Putin warned Kiev of “consequences” if it continued to use force in the east of the country.

Russia has some 40,000 troops on its border with Ukraine. On Wednesday, 150 US troops arrived in Poland to bolster security along the European Union’s eastern flanks. Another 450 troops are due to join the first contingent in Poland, Estonia, Latvia and Lithuania in the coming days.

The US accuses Russia of backing separatists in eastern Ukraine as part of a deliberate attempt to destabilize the region, undermine elections planned for next month, and gain greater influence over Kiev.

Additional reporting by agencies