Indonesia (search) warned aid workers Sunday that separatist rebels had infiltrated camps sheltering survivors of the Dec. 26 tsunami as fears escalated that the stricken area's long-simmering insurgency could hamper efforts to help victims of the 2-week-old disaster.

Violence in tsunami-ravaged Sri Lanka (search) also revived security fears for aid workers setting up operations there. Christians and Hindus clashed in the eastern part of the country, where a massive aid effort is underway. At least three people were killed and 37 injured.

In Banda Aceh (search), gunfire echoed through the main tsunami-hit city on Indonesia's Sumatra island Sunday. Indonesian authorities blamed separatist rebels for the shooting near the U.N. compound in Banda Aceh.

No aid workers were injured in either incident.

Two weeks after walls of water flattened wide swaths of coastland around the Indian Ocean, people were still emerging from isolated villages and bodies were being pulled from the mud and debris as the death toll in 11 countries passed 150,000.

Relief workers poured into the region as aid officials announced plans to feed as many as 2 million survivors a day for the next six months, focusing particularly on young children, pregnant women and nursing mothers.

The ethnic conflict in Sri Lanka overshadowed the visit of U.N. Secretary-General Kofi Annan to tsunami-devastated areas there. Hundreds of people protested in the Tamil-dominated north Sunday after Annan acceded to a government request not to visit stricken areas under Tamil rebel control.

"I'm hoping to come back and be able to visit all areas of the country, not only those repaired, but also to celebrate peace," Annan said. "The U.N. is not here to take sides."

The Tigers have fought a 20-year war for Tamil independence from the Sinhalese-dominated south, killing thousands.

There was an unofficial truce after last month's disaster, which left more than 100,000 dead in the province, but a series of recent skirmishes have prompted Indonesia's military to step up patrols for the guerrillas.

The Indonesian government warning offered no details about the infiltrations but came just hours after police in the provincial capital, Banda Aceh, blamed the separatists for a burst of gunfire close to the main U.N. compound in the town.

Citing military sources for the reports of rebels mingling with refugees, military spokesman Ahmad Yani Basuki told the state-run Antara news agency that volunteers must understand that "this is still a conflict-torn region."

U.N. officials in Indonesia downplayed the Banda Aceh shooting, which took place near the home of a deputy provincial police chief, saying there was no indication the gunfire targeted efforts to feed the disaster's hungry and homeless.

"We don't believe that aid workers are targets," said Joel Boutroue, a U.N. relief official in Aceh. "We were told by guards that it was probably one person shooting a few rounds and that was it."

Indonesian officials regularly blame Free Aceh Movement rebels for shootings and violence in Aceh, even if there is sometimes little evidence of their involvement.

Adding to security concerns is the appearance of Laskar Mujahidin, an extremist group with alleged links to Al Qaeda. The group, which has set up an aid camp, says it is there to help and will not target foreigners, but its reassurances have not dampened worries.

But aid workers kept arriving, with the World Food Program sending 170 staff members. Other agencies have similar numbers.

World governments, led by Australia and Germany, have pledged nearly $4 billion in aid — the biggest relief package ever. The United States has pledged $350 million, which President Bush called only an "initial commitment" while American relief officials identify needs.

The U.S. military, which has hundreds of Marines and Navy personnel on ships near Sumatra and in Sri Lanka, said aid workers must remain vigilant while working in restive areas.

"Security is a constant planning factor in all that we do," U.S. Army aid coordinator Maj. Nelson Chang said.

Rain pounded relief workers Sunday, turning Banda Aceh airport — the hub for aid supplies — into a muddy mess and soaking piles of cardboard boxes of aid sitting on the tarmac. Scores of tents where aid workers and soldiers camped had become a quagmire.

The rainy season downpours could complicate a relief effort already hamstrung by damaged roads and bridges washed away.

Refugee camps are being built on Sumatra to house and feed half a million homeless people.

World leaders have been streaming into the region to better assess the needs of survivors.

"The world is responding rather well, but there should be no illusion as to how long it's going to take to rebuild these communities," Secretary of State Colin Powell said on ABC's "This Week" program from Nairobi, Kenya. But he said "people are not starving. There is food in the region."