Tensions in Ukraine flare as EU calls for groups to lay down weapons

“All parties to the joint Geneva Statement on Ukraine of 17 April must ensure that its terms are fully implemented,” he said.

The agreement calls upon all illegal armed groups to disarm, vacate illegally seized buildings and occupied streets, squares and other public places in Ukrainian cities and towns.

His US counterpart Secretary of State John Kerry in Washington accused Russia of "distraction, deception and destabilisation" in eastern Ukraine.

Kerry said Russia is not abiding by the Geneva statement.

“Not a single Russian official, not one, has publicly gone on television in Ukraine and called on the separatists to support the Geneva agreement,” he said.

Kerry said Russia needs to implement its side of the agreement or risk facing additional sanctions.

“If Russia continues in this direction, it will not just be a grave mistake, it will be an expensive mistake,” he said.

But key government buildings in dozens of eastern Ukrainian towns remain occupied by pro-Russian separatists.

At least two separatists were killed following raids by Ukraine forces earlier in the week on pro-Russian checkpoints around Sloviansk.

"If the regime in Kiev has begun using the army against the population inside the country, then this is undoubtedly a very serious crime," President Putin told Russian media.

The raids provoked new Russian military exercises along the border on Thursday. Russia has around 40,000 troops amassed next to Ukraine.

Ukraine's acting president, Oleksandr Turchynov, said Russia must pull back its forces and “stop the constant threats and blackmail”.

EU foreign affairs chief Catherine Ashton, for her part, said the latest news from Eastern Ukraine on reported kidnappings, torture and killings is “a cause for grave concern”.

Kiev last week accused Moscow of the murder of a regional Ukrainian politician.

Meanwhile, unnamed sources told Reuters the US is set to discuss imposing additional sanctions in a conference call on Friday with British Prime Minister David Cameron, French President Francois Hollande, German Chancellor Angela Merkel and Italian Prime Minister Matteo Renzi.

Mann, for his part, noted discussions to impose any additional sanctions is “an on-going process which requires a lot of work and co-operation with our member states”.

EU foreign ministers are set to meet to discuss Ukraine on 12 May.