KIEV (Reuters) - At least four Ukrainian servicemen and five coal miners were on Friday reported killed in the latest violence in the east of the country, where government forces are fighting pro-Russian separatists.

The miners were killed after the bus they were traveling in came under mortar fire, Ukrainian television reported a doctor as saying, in the region of Chervonopartizansk near the border with Russia.

Two soldiers and at least one border guard were killed after their armored vehicle drove over a landmine near Dovzhansky on Ukraine’s border with Russia.

Military spokesman Vladyslav Seleznyov said a soldier was also killed in an incident near the town of Karlovka in the region of Donetsk, the main city where rebel fighters are holding out against the government forces.

He said at least 50 separatist fighters had been killed in the last few days following air strikes against rebel positions near the border with Russia.

There was no immediate comment from the rebels.

The shelling of the bus forced energy and coal processing company DTEK, which employed the miners, to suspend operations at four mines in the economically depressed industrial province of Luhansk, Interfax news agency quoted the company’s general director as saying.

The government forces have gained the upper hand in the three-month-old conflict in the Russian-speaking eastern regions in which more than 200 government troops have been killed as well as hundreds of civilians and rebel fighters.

In diplomacy to end the worst Russia-West crisis since the Cold War, French President Francois Hollande and German Chancellor Angela Merkel urged Russian President Vladimir Putin by telephone on Thursday to exert pressure on the separatists to de-escalate the violence.

Ukrainian President Petro Poroshenko told U.S. Vice President Joe Biden that Russia and Ukrainian separatists had refused multiple proposals by Kiev for venues to negotiate a ceasefire, the White House said.

Rebels armed with heavy machine guns took positions late on Thursday around the airport controlled by Ukrainian forces in the industrial hub of Donetsk. Shots were heard overnight.

“Last night for an hour there was shelling against Ukrainian servicemen at the Donetsk airport,” Seleznyov wrote on his Facebook page.

Poroshenko has ruled out air strikes and artillery bombardment because of the large civilian population in Donetsk.

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Bt the Ukrainian military say they have a plan to deliver a “nasty surprise” to the rebels and take back their main strongholds, Donetsk and Luhansk.