By Gyles Beckford and Lincoln Feast

WELLINGTON/SYDNEY, March 16 (Reuters) - The first reports from the outer islands of Vanuatu on Monday painted a picture of utter destruction after a monster cyclone tore through the Pacific island nation.

Authorities in the South Pacific nation were struggling to establish contact with the islands that bore the brunt of Cyclone Pam's winds of more than 300 kph (185 mph), which flattened buildings, smashed boats and washed away roads and bridges as it struck late on Friday and into Saturday.

The government's official toll is eight dead and 20 injured but that looks certain to rise, given the extent of the damage.

The southern island of Tanna, about 200 km (125 miles) south of the capital, Port Vila, with its 29,000 inhabitants took the full force of the category 5 storm.

Early reports from aid groups said it had been devastated, along with the main town on the southern island of Erromango.

A clean-up was under way in Port Vila, where seas were reported to have surged as high as 8 metres (26 feet), with as much as three-quarters of the capital's houses reported destroyed or severely damaged.

"It just looks like a bomb has gone off in the centre of town," said Alice Clements of Unicef from Port Vila.

"The trees are shredded, there are power lines everywhere, the corrugated iron has been wrapped into strange shapes by the force of the wind."



Red Cross Vanuatu CEO Jacqueline de Gaillarde said shops were already low on supplies because people had stockpiled food before the storm but those supplies were then lost when homes were destroyed.

"We need food for the coming weeks and we need humanitarian people to do assessments and we need transport, we need boats to access the islands because lots of the airports on the islands are grass only and they are flooded so we cannot land," de Gaillarde told Reuters by telephone from Port Vila.

The Red Cross had been in touch with staff in Torba province in Vanuatu's north, were people were reported to be safe. Earlier unconfirmed reports had said more than 40 may have been killed in the northern region.

Diseases including dengue fever and malaria were a concern with widespread flooding and housing damaged or non-existent, she said.

"People are coming to sleep in shelters at night and in the morning going to back to their properties to protect their belongings," she said.

Military flights from New Zealand and Australia were bringing in water, sanitation kits, medicines and temporary shelters for the estimated 10,000 made homeless on the main island.

Commercial flights were also due to resume on Monday to bring in more aid and take out tourists.

Formerly known as the New Hebrides, Vanuatu is a sprawling cluster of 83 islands and 260,000 people, 2,000 km (1,250 miles) northeast of the Australian city of Brisbane.

Among the world's poorest countries, Vanuatu is rated the world's most vulnerable out of 111 countries on the Commonwealth Vulnerability Index. Perched on the geologically active Pacific Ring of Fire, it suffers from frequent earthquakes and tsunamis and has several active volcanoes in addition to threats from storms and rising sea levels.

Aid officials said the storm was comparable in strength to Typhoon Haiyan, which hit the Philippines in 2013 and killed more than 6,000 people, and looked set to be one of the worst natural disasters the Pacific region has experienced.

Australia promised A$5 million in aid and New Zealand NZ$2.5 million. Britain, which jointly ruled Vanuatu with France until independence in 1980, has offered up to two million pounds ($2.95 million) in assistance.

"We have made a substantial start but of course it's early days so we have to assess the damage," Australian Foreign Minister Julie Bishop told ABC TV. "This will be an ongoing operation over a number of days, weeks, months ahead."

The World Bank said it was exploring a swift insurance payout to the government, and the International Monetary Fund said it was ready to send funds and assistance to rebuild Vanuatu's economy.

Pam was losing its intensity as it passed by the east coast of New Zealand's North Island, where it was bringing strong winds, rain, and big seas but so far little damage. (Editing by Alison Williams and Paul Tait)