SUVA, Fiji — Fiji declared a state of emergency today and ordered troops to launch relief operations in northern regions battered by a powerful cyclone that knocked out power and forced thousands of people to flee into shelters.

Cyclone Tomas’ onslaught began to weaken today, but the scope of destruction was not clear because communications were cut to the outer islands and to northern areas of Vanua Levu, the group’s second-biggest island, that were hardest hit, officials said.

One death has been reported, and a nationwide curfew was still in effect.

Fiji’s National Disaster Council declared a 30-day state of emergency for the country’s northern and eastern divisions today, ordering troops to be deployed as soon as possible to provide relief, including food, water and basic supplies.

Packing winds of up to 130 mph at its center, and gusts of up to 175 mph, Cyclone Tomas continued today to blast through the northern Lau and Lomaiviti island groups and the northern coast of Vanua Levu, the nation’s weather office said.

Matt Boterhoven, Fiji’s Tropical Cyclone Center’s senior forecaster, said Tomas was still a Category 4 storm, but was expected to weaken to Category 3 by late today as it moves into the open sea south of the island group.

Sea surges of up to 23 feet were reported in the Lau island group, which was hit head-on by the cyclone, causing major flooding, Boterhoven said, adding that the surges would take at least 36 hours to subside.

Rain had drenched northern areas with up to 14 inches over two days and was still falling.

National Disaster Management Office spokesman Anthony Blake said power, water, sewage and other services were disrupted in many northern areas, with all airstrips and airports closed and storm surges smashing into coastal villages and schools. More than 17,000 people were in 240 government shelters, he said.

Initial damage assessments will likely be made Wednesday, when airplanes are expected to survey the northern islands and Vanua Levu, Blake said.

The country’s military leader, Commodore Frank Bainimarara, has appealed for international assistance, New Zealand Foreign Minister Murray McCully said, and the governments of New Zealand, France and Australia were trying to determine how best to help. The New Zealand air force was on standby to fly emergency supplies to Fiji and assist with aerial reconnaissance.

The capital, Suva, has been lashed by high winds and rains, and the government extended a nationwide curfew to Wednesday morning to keep people in their homes.

By this afternoon, flights had resumed into the main international airport at Nadi, on the main island of Viti Levu. There were no immediate reports of tourists being caught in the cyclone.

Late Friday, a 31-year-old woman was swept away by strong ocean currents in Vanua Levu’s Cakaudrove province after she saved her two children from a storm surge, police spokeswoman Atunaisa Sokomuri said.