Six Ukrainian soldiers have been killed by pro-Russian rebels in the last 24 hours, a government official said Saturday.

"Our losses as a result of fighting were six servicemen killed and 10 wounded," Volodymyr Polyovy, spokesman for the National Security and Defence Council, said.

Polyovy said the deaths showed that separatist forces "continue to violate the ceasefire agreement" signed September 5, but increasingly in tatters.

One of the main attacks took place at the ruins of Donetsk airport, which remains partly in Ukrainian hands, despite lying in territory mostly controled by the separatists.

"The terrorists attacked the positions of Ukrainian soldiers six times with rocket grenades, mortars, anti-aircraft weapons and small arms," he said.