SUVA - The first batch of international relief supplies arrived in cyclone-ravaged Fiji Wednesday as military leader Voreqe Bainimarama spoke of "overwhelming" damage to the Pacific island nation.

Category-four Cyclone Tomas - the second strongest on a five-point scale - devastated areas in the north and east of Fiji but has weakened and is moving away from the south, allowing officials to assess damage.

Communications with many of the affected areas were cut as winds averaging up to 175 kilometres (109 miles) an hour and waves caused by storm surges slammed into Fiji on Monday and Tuesday.

Fiji-based Pacific deputy representative for UNICEF Tim Sutton said about 150,000 Fijians had potentially been directly affected by the powerful cyclone, with Bainimarama describing the damage late Tuesday as "overwhelming."

National Disaster Management Office director Pajiliai Dobui said there were unconfirmed reports of a "few" deaths.

"Those who have experienced other cyclones say this is the longest and the strongest they have come across - and the most destructive," Dobui said.

A state of emergency was declared for the north and east on Tuesday, opening the way for foreign assistance to be brought into areas where homes, crops and infrastructure have been destroyed.

A New Zealand Air Force C130 Hercules arrived in Fiji Wednesday morning with relief supplies with another Hercules from Australia due later in the day.

The aircraft were expected to carry out surveys of the damage and Fijian officials said a French plane was also expected to be involved in surveying devastated areas.

Australia and New Zealand also pledged one million Australian dollars and one million New Zealand dollars (totalling 1.6 million US) as initial contributions to the aid effort.

Australian Foreign Minister Stephen Smith said the two countries would coordinate their response.

"Australia will consider further assistance for reconstruction once damage has been more fully assessed," he said.

Fiji's National Disaster Management Office operations officer Anthony Blake said late Tuesday there was a need for tents and emergency shelters, water containers and purification tablets and emergency morgues.

Two Fiji Naval Squadron boats and three other ships were due to take relief supplies to the Lomaiviti and Lau islands in the east on Wednesday, he said.

UNICEF's Sutton said his organisation was dispatching emergency supplies, including water containers and purification tablets to affected areas.

"Our focus at the moment is getting our supplies in our warehouse in Suva onto boats and up there as quickly as possible," Sutton told AFP.

The situation was unclear Wednesday but it was clear a lot of international help would be needed, he said.

"It's going to take three, four or five days until you get a decent picture of what happened."