KIEV - Ukraine has announced a unilateral ceasefire in eastern regions to allow armed activists to lay down their weapons or leave the country.

"From our side, we will offer amnesty to those insurgents who will lay down their arms and those who have not committed serious crimes," President Petro Poroshenko told reporters here Wednesday.

The ceasefire period would be "very short", Poroshenko said, without specifying an exact timeframe.

Poroshenko stressed the importance of ensuring the safety of civilians in crisis-hit regions, urging the rebels to immediately release hostages, abandon seized buildings and carry out full disarmament.

To restore order in the battle-torn areas, Ukrainian authorities were ready to make further concessions to the insurgents, including comprehensive constitutional reform that would strengthen the regions' powers, Poroshenko said.

He also pledged to unveil his comprehensive 14-point peace plan to end the anti-government protests in Donetsk and Lugansk regions in days.

Kiev started its military operation against insurgents in mid-April in an attempt to retake control of the cities and towns seized by armed activists, who declared independence from Kiev.

The protest in the mostly Russian-speaking eastern part of Ukraine started shortly after the ouster of former President Viktor Yanukovych in February as a peaceful movement to demand more autonomy.

Later, the protest snowballed into violent unrest, with insurgents demanding their region split from Ukraine. So far, more than 260 people have died in clashes between government troops and rebels in eastern part of the country.