Bloodshed mounts in eastern Ukraine

KIEV, Ukraine -- Prospects for Ukraine peace talks remained dim Friday as hostilities intensified between government forces and Russian-backed separatists in the east.

The escalation in fighting has centered on the key flashpoint, the airport of the rebel stronghold Donetsk, where rebel militia have renewed efforts to dislodge government troops. Separatists say they have almost total control over the civilian terminal, but Ukrainian troops say they still hold parts of the building.

A spokesman for the Ukrainian military, Andriy Lysenko, said six troops had been killed "as a result of combat activity and another 18 have been wounded in the past 24 hours," according to the Reuters news agency.

Representatives from Ukraine and Russia, separatist envoys and officials of the Organization for Security and Cooperation in Europe were tentatively set to hold talks Friday in Minsk, Belarus, on ensuring a cease-fire to be monitored by the OSCE.

Residential areas in Donetsk remain caught in the artillery crossfire. Separatist authorities in Donetsk said four people died in a fire Thursday after a warehouse was hit by a shell.

The U.N. estimates that more than 4,700 people have been killed in eastern Ukraine since April, and fighting has continued despite September's cease-fire deal that included a provision to pull back heavy weapons.

A demarcation line, also agreed in that deal signed in Minsk, has been routinely flouted.

The U.S. Embassy in Ukraine accused the rebels of violating the boundary.

"The separatists have pushed their lines well beyond the territorial lines agreed upon in Minsk," Ambassador Geoffrey Pyatt said in an emailed statement.

Government officials and rebels have reported fighting along a front extending more than 350 kilometers (220 miles).

A fresh truce was announced in December, only to unravel last week and derail a planned meeting of the leaders of Ukraine, Russia, France and Germany in Kazakhstan this week.

Ukraine says separatist forces are accumulating along the front line.

Military spokesman Andriy Lysenko said rebels have mobilized large numbers of armored vehicles in the past few days, with a particular concentration noted in Horlivka, a city east of Donetsk.

"In Horlivka, there is a three-kilometer long column of tanks heading in the direction of Ukrainian positions," he said.