Military Helicopter shot down

Olexander Turchynov said the rebels used a Russian-made anti-aircraft system, and a senior general was among the dead.

The town of Sloviansk has seen fierce fighting between separatists and government forces in recent weeks.

President-elect Petro Poroshenko has vowed to tackle "bandits" in the east.

The helicopter was hit during heavy fighting between Sloviansk and Kramatorsk, reportedly after it had dropped off troops at a military base.

President Turchynov said the 14 dead included Gen Serhiy Kulchytskiy, head of combat and special training for Ukraine's National Guard.

It is one of the worst losses of life for government forces in the conflict so far. Last week at least 14 soldiers died in a rebel attack on an army checkpoint near Donetsk, some 130km (80 miles) from Sloviansk.

Earlier this month the separatists shot down two army helicopters, also near Sloviansk, killing a pilot and another serviceman.

This is a significant blow for the Ukrainian military and the government in Kiev as it pursues what it calls its "anti-terror operation" in the east. Sloviansk, a town taken by the rebels early in this uprising, has long been the epicentre of the heaviest fighting here.

Two other Ukrainian helicopters were downed there at the start of May, a reminder that Kiev is not simply facing an amateur group of fighters here.

This has been a week in which the conflict in eastern Ukraine has escalated. After Kiev launched an air-and-ground assault on separatist groups at Donetsk airport to retake control, the rebels have vowed to regroup.

They hold patches of land and are clearly equipped with significant weapons. When Ukraine's new President-elect, Petro Poroshenko, vows to crush what he calls the "terrorists" within "a few hours, rather than a few months", this latest loss of life illustrates the immense challenge he faces.