Sri Lanka's military has urged about 250,000 civilians in an area held by Tamil Tiger separatists to cross into a "safety zone" in government-controlled territory.
The Sri Lankan air force on Wednesday dropped leaflets in the region telling civilians to move to the 35sq km zone until the army can transport them to safer locations.
"We will not fire into that area," Brigadier Udaya Nanayakkara, a military spokesman, said.
It was unclear how the refugees would be transported out of the small territory in the north, the only remaining area controlled by the Tamil Tigers after a military offensive aimed at ending the 25-year civil war.
The government says it has set up temporary shelters in the Vavuniya area, south of the fighting, where food and water will be provided.
Human rights groups have raised concerns for the safety of people living under siege in the shrinking territory.
New York-based Human Rights Watch accused the separatists of preventing people from fleeing, while the Tigers say they are protecting civilians who voluntarily move with them.
Meanwhile, at least two people were killed and 11 others injured in a roadside bomb attack in eastern Sri Lanka.
The Tamil Tigers were suspected of being responsible for Wednesday's blast, police officials said.
The explosion occurred in the town of Batticaloa, about 300km east of Colombo, the Sri Lankan capital.
A policemen and another civilian were killed in the blast when a bomb planted on a bicycle went off.
Eleven civilians, including six children, were also injured, according to police officials.
The separatists could not be reached for comment.
The attack came a day after government forces killed about 16 Tiger fighters in a naval attack near Mullativu, the fighters' last base, off the northeastern coast of the country.