Sri Lankan troops on Friday took more Tamil Tiger bases in their final push against the cornered rebels, as UN chief Ban Ki-moon raised fresh concerns for the safety of civilians in the war zone.
Security forces seized a large quantity of automatic assault rifles, detonators and hand grenades from two camps of the Liberation Tigers of Tamil Eelam (LTTE) in the district of Mullaittivu, a military official said.
"Clearing operations are now under way," the official said, adding that troops were consolidating their hold on the Chalai Sea Tiger base, which was taken on Thursday.
With the fall of Chalai, the Tigers only have access to 20 kilometres (12 miles) of coastline in the northeastern district.
Military officials said the total area under rebel control had shrunk to just 200 square kilometres and as fighting intensified, international concern over the fate of civilians trapped in the zone also heightened.
Ban telephoned President Mahinda Rajapakse on Thursday to discuss the plight of the civilians and was given an "assurance" that they would not be harassed, a government statement said.
The United Nations, which has a presence in the island's embattled areas, reported at least 52 non-combatants were killed in a single shelling incident earlier this week -- though it did not say who was responsible.
The main hospital in the war zone was evacuated on Wednesday after repeated shelling in the area and another rural medical centre was preparing to move away on Friday, medical sources said.
The government had ordered doctors to move the hospitals to safer government-held areas in the region, but aid workers said the guerrillas had prevented the relocation.
International rights groups and foreign governments have urged the Tigers to allow civilians safe passage, but Sri Lanka's key foreign aid donors acknowledged on Tuesday that they had failed to secure rebel agreement.
Doctors said some rural hospitals had dead bodies with no relatives to claim them because of the fighting in the area.
The United States, the European Union, Japan and Norway asked the rebels to lay down their arms and take part in a political dialogue to end the bloodshed and save the lives of civilians as well as combatants.
In a statement, Sri Lanka's foreign ministry on Thursday night welcomed the calls, while stressing that it was the LTTE who had been preventing civilians from getting out of the conflict zone.
"The government notes the timely call to the LTTE to lay down arms," the ministry said, adding that it had repeatedly called on the rebels to surrender their weapons and join the democratic process.
Defence Secretary Gotabhaya Rajapakse had a more hawkish response, insisting that nothing short of "unconditional surrender" could bring an end to the military offensive.
Sri Lanka has brushed aside previous international appeals for a ceasefire and vowed to finish off the guerrillas, who have been leading a campaign for a separate state for minority ethnic Tamils since 1972.