A Russian jet has shot down a Ukrainian SU-25 attack plane over the east of Ukraine, a Ukrainian military spokesman has said.

Andriy Lysenko, a spokesman for Ukraine's national defence and security council, said on Thursday that the plane was shot down on Wednesday night by an air-to-air missile but the pilot safely ejected.

According to the Reuters news agency, it was the third reported incident this week in which a Ukrainian plane has been hit by a missile.

Earlier this week, officials in Kiev said that a Ukrainian military transport plane had been shot down on Monday along the country's eastern border with Russia.

Two out of the eight people on board that plane were killed, the Ukrainian military said.

Ukrainian officials blamed Moscow for the attack. Moscow denies it is supporting the separatists.

Russia has not commented on the latest reported attack.

Pro-Russia rebels, meanwhile, said they fired on two other Ukrainian SU-25 jets, the AP news agency reported.

The defence ministry said the second jet was hit by a portable surface-to-air missile, but added that the pilot was unhurt and managed to land his plane safely.

Lysenko said five more Ukrainian servicemen had been killed in the past 24 hours, which would bring to more than 270 the number killed since the government launched its operation in the east in April.

After a day's pause, Ukrainian jets on Wednesday resumed overflights in the east where they have been striking at concentrations of rebels and military equipment, which Kiev says is being brought in from Russia to fortify rebel positions.