A United Nations-led effort to consolidate international aid to the tsunami-stricken Solomon Islands began Sunday as frightened villagers descended from the hills to celebrate the Easter holiday.

A team of UN disaster experts arrived in the Solomon Islands during the weekend to help the national government coordinate its response to last week’s earthquake and tsunami that flattened several villages and killed more than two dozen people.

Disaster coordinator Paul Muller said the UN was reviewing all available data to determine which islands and villages had still not been reached by international aid teams that have been delivering food, tarpaulins and other supplies since the local airstrip reopened.

Meanwhile, helicopters continued to buzz in and out of Gizo, the region’s main population center, as aid workers delivered supplies and medical care to outlying islands.

The International Red Cross and other aid groups have deemed basic latrines and water purification systems a top priority, in a frantic bid to stop the spread of disease.

A few isolated cases of dysentery and diarrhea have been reported in the hills above Gizo, but officials say they are optimistic about preventing widespread outbreaks of diarrhea, dysentery and cholera.

Nevertheless, thousands of villagers were still huddled in unhygenic refugee camps in the hills above their ruined towns on Sunday, too frightened to come down.

Despite their fears, more than 100 villagers left their hillside camps to celebrate an Easter service at St. Luke’s Anglican church on the outskirts of Gizo.

They said prayers for the dead, and sang traditional hymns in a concrete church decorated with tropical flowers and palm leaves. Arebonato was trying to get her 3-year-old twin girls ready for school when the earthquake struck, knocking her from her feet.

Tsunami waves appeared almost immediately, she said, and she grabbed her children and ran to the hills. She said many locals do not understand what caused the earthquake and tsunami.

“Maybe it’s a punishment from God,” she said. “Before, there were few people in church. Now, after (the) earthquake, the church is filled with people, some of them never went to church before.”

Solomon Islanders are predominantly Christian, and at least five churches of various denominations dot the hillsides around Gizo. The Roman Catholic Church was knocked down by the quake, but devotees gathered in the garden for their own Easter ceremony.