COLOMBO, Sri Lanka - The visiting French and British foreign ministers urged Sri Lanka to accept a cease-fire Wednesday in its war with ethnic Tamil rebels, saying it needed to act quickly to save the lives of civilians in the war zone.

The government has repeatedly rejected calls for a truce, saying any pause in its battle against the Tamil Tigers would give the rebels time to regroup.

"Now is the time for the fighting to stop," British Foreign Secretary David Miliband told reporters in Colombo. "Protection of civilians is absolutely paramount in our minds."

Miliband and French Foreign Minister Bernard Kouchner were on a hastily planned daylong visit to Sri Lanka to express international concern for the fate of the estimated 50,000 civilians still trapped in the war zone.

The call for a cease-fire was not intended to protect the remaining rebels and their reclusive leader Velupillai Prabhakaran, but to safeguard the civilians there, Miliband said. The ministers also accused the rebels of holding the civilians as human shields and demanded they release them.

In recent weeks, reports from the area outlined growing civilian casualties and cases of starvation.

The two diplomats, acting as EU envoys, met Sri Lankan Foreign Minister Rohitha Bogollagama and called on the government to allow aid workers into the war zone. Kouchner said the government denied that request, though it agreed to give aid workers access to other parts of the north.

Miliband and Kouchner later toured displacement camps overwhelmed by an influx of an estimated 120,000 war refugees in the past 10 days.

Thousands of displaced people gathered along the road as Miliband visited three camps near the northern town of Vavuniya. Many told Miliband that conditions in the camps were better than the dire situation they faced in the war zone.

One woman complained that her husband and son had been detained by authorities. She was told they would be released after a six month rehabilitation program.

The diplomats were also to meet Sri Lankan President Mahinda Rajapaksa.

The pair were among the highest-level European officials to visit the island since the aftermath of the 2004 tsunami. The UN humanitarian chief traveled here over the weekend and expressed similar concerns about civilians. The UN says nearly 6,500 civilians have been killed in the government's recent offensive.

Many Sri Lankans bristle at outside interference in the fighting, and more than 100 people, led by a group of ultranationalist Buddhist monks, protested outside the British Embassy in Colombo to demand Miliband leave immediately.

The government said Monday that it would stop firing heavy weapons into the tiny coastal strip where the rebels are surrounded because of the risk of civilian casualties. But a rebel-linked Web site and health officials in the area accused the military of launching a fierce barrage of artillery and mortar shells Tuesday morning that killed at least 11 civilians.

Defense spokesman Keheliya Rambukwella said the government had not used heavy weapons in two weeks. Journalists and aid groups are barred from the war zone, making reports of the fighting difficult to verify.

The beleaguered rebels declared a unilateral cease-fire Sunday, but the government rejected it as a play for time.

Rambukwella said the truce was a bluff and cited seven rebel suicide attacks -- one by car, two by motorbike and four by pedestrians -- in the war zone Tuesday.

Meanwhile, the navy destroyed six rebel boats -- four of them suicide craft laden with explosives -- off the coast early Wednesday, killing at least 25 rebels, the military said in a statement.

The Tamil Tigers, listed as a terrorist group by many Western nations, have been fighting since 1983 for an ethnic Tamil state in the north and east after decades of marginalization by governments dominated by the Sinhalese majority.

Meanwhile, the UN High Commissioner for Refugees expressed concern for the welfare of the war refugees in government-run camps. The agency said it had airlifted 5,000 tents and other relief supplies to Sri Lanka and were bringing in extra staff to monitor the sites.

"The conditions at the sites have reached breaking point, placing severe strains on the humanitarian services available. People without shelter are staying out in the open in the blazing sun and sweltering heat," the agency said in a summary of a press briefing Tuesday in Geneva.

The agency called on the government to provide more public buildings and land for the displaced and to separate former rebels from the civilians so they can be rehabilitated.