Kiev, June 5 (IANS): President Petro Poroshenko said on Friday that Ukrainian forces have completely liberated the village of Marinka, where pro-Russian separatists had launched an offensive, and that a Russian citizen has been arrested, Efe news agency reported.

"On June 3, a clean-up operation was carried out... As a result, today I can announce that Marinka has been completely liberated from saboteurs. Twelve people have been arrested, including a Russian," Poroshenko said at a press conference in Kiev.

He added that the fighting in that area of the Donetsk region, which erupted this week with clashed between Ukrainian forces and pro-Russian militias, has been the most serious since a ceasefire reached in Minsk in February.

Poroshenko condemned that between 500 and 1,000 militants attacked Marinka with tanks and armoured vehicles, adding that the intent of the militias to provoke an escalation of the conflict coincided with Moscow's threat to authorise the entry of Russian troops to Ukraine.

The Ukrainian president noted that the level of threat of a Russian invasion was extremely high, and for that reason, 50,000 Ukrainian soldiers have been deployed in the conflict zone.

Poroshenko also stated that he would speak on Friday on the phone with US President Barack Obama and German Chancellor Angela Merkel to coordinate their positions ahead of the G7 summit, which to be held this weekend in Munich.