RANGOON, Burma — U.N. helicopters loaded with relief supplies reached areas of Burma’s Irrawaddy delta yesterday that have been cut off from regular aid since a devastating cyclone five weeks ago, an official said.

Four of the five aircraft that arrived over the weekend got to work shuttling emergency supplies like rice and water purification systems to villages around the hardest-hit towns of Bogale and Labutta, a U.N. World Food Program spokesman, Paul Risley, said.

A total of four flights flew yesterday to seven locations in the delta and six more sites were expected to be reached today, he said.

U.N. officials and aid groups have criticized Burma’s military regime for restricting access to the delta, saying it has prevented enough food, water, and shelter from reaching desperate survivors.

Until now, the United Nations had only one helicopter operating in Burma that flew a total of six trips last week, Mr. Risley said. Supplies were mainly being delivered by boats that took several hours to navigate short distances in the delta’s network of waterways.

Four more helicopters chartered by WFP, which are currently in neighboring Bangkok, Thailand, are expected to fly to Burma this week.