The International Committee of the Red Cross is evacuating 400 sick and wounded civilians who had been trapped by fighting in north-east Sri Lanka.
An ICRC spokeswoman told the BBC the evacuees would be taken by ferry to the city of Trincomalee for treatment.
The ICRC said the group had been stranded at a makeshift hospital in Mullaitivu district for nearly a week.
Earlier more civilians were reported killed as intense fighting continues between troops and Tamil Tiger rebels.
The Red Cross says the recent fighting has claimed hundreds of civilian lives and tens of thousands more are trapped.
On Monday, the military said 29 people died when a female Tamil Tiger rebel blew herself up in the north-east.
Independent journalists cannot travel to the war zone so information cannot be verified.
‘Safe passage’
Sarasi Wijeratne, an ICRC spokeswoman in Colombo, said a ferry chartered by the ICRC had arrived from Jaffna on Tuesday morning to pick up 400 patients from the coastal village of Putumattalan.
"The sick and wounded are being put on the ferry," she told the BBC Sinhala service.
She said both sides in the conflict had agreed to allow patients to be moved for treatment.
"We were requesting safe passage from the parties to the conflict and the parties are in agreement about this evacuation."
Earlier, Sri Lankan military spokesman Brig Udaya Nanayakkara said that civilians heading into government-controlled areas told soldiers that rebels had fired on a group of 1,000 people who were trying to flee the fighting.
"The civilians came to an army position carrying the 17 dead and 69 others who had gunshot injuries," Brig Nanayakkara said.
The government says thousands are trying to cross to safety each day and accuses the rebels of using civilians as human shields.
The pro-rebel TamilNet web site also says thousands are fleeing but that they are seeking shelter in Tiger-controlled areas because of army shellfire into the government-declared "safety zone".
It said at least 36 civilians were killed and 76 wounded because of military mortar and artillery fire.
The ICRC has expressed serious concern for more than 200,000 trapped civilians. The government says the number is about half that.
Both the UN and US condemned Monday’s killings in the Vishwamadu area of Mullaitivu district.
A UN statement reiterated that "civilians must be distinguished from combatants and protected from the fighting". The US embassy said it was an "apparent effort by the [Tamil Tigers] to discourage Tamils from leaving the conflict area".
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