Donetsk (Ukraine) (AFP) - Two Ukrainian soldiers and two rebels have been killed in eastern Ukraine, marking the first deaths this year in the war-torn region, Kiev and breakway officials said Sunday in separate tolls.

"Over the last day, two Ukrainian soldiers have been killed", military spokesman Oleksandr Motuzyanyk told reporters, despite a wobbly truce between the pro-Russian rebels and government forces still largely holding.

A Ukrainian police officer fighting in the Mirotvorets volunteer battalion was killed in shelling near the village of Zaitseve, some 55 kilometres (35 miles) northeast of the rebels' de facto capital Donetsk.

He died as he tried to stop a car carrying civilians and prevent it from coming under fire. A woman in the car was wounded.

The other victim was a soldier in the Ukrainian armed forces who received multiple shrapnel wounds as a result of grenade fire in the same area, Motuzyanyk said.

Meanwhile, separatist authorities said one of their military commanders was killed, possibly shot by a sniper.

"Colonel Yevgeny Kononov was killed at the front. I can't say yet whether it was a sniper bullet, but our front is everywhere now", military spokesman Eduard Basurin told AFP.

Rebel news website Russkaya Vesna, or Russian Spring, said Kononov had been active in key battles in the conflict that has killed more than 9,000 people since April 2014, fighting at flashpoints such as Ilovaisk, Debaltseve and Donetsk airport.

A second rebel fighter was killed by a Ukrainian sniper while on combat duty in Zaitseve on Saturday evening, the separatist DAN news agency said.

Ukraine and pro-Russian insurgents agreed a vital New Year's truce that went into effect on December 23 in the hope of finally ending clashes in the war-scarred ex-Soviet state.

A series of truce agreements have helped to significantly reduce the fighting, although sporadic clashes continue on the frontline.