Vanuatu's president said climate change was partially to blame for the "monster" cyclone that devastated the archipelago nation in the Pacific.

Six people were confirmed killed and 30 injured by the category-five storm named Pam, which struck the tiny state's 65 islands on the morning of Saturday 14 March.

"This is a very devastating cyclone in Vanuatu. I term it as a monster, a monster," President Baldwin Lonsdale said as he attended a UN disaster conference in Japan.

"It's a setback for the government and for the people of Vanuatu. After all the development that has taken place, all this development has been wiped out."

The death toll was expected to rise sharply, as the cyclone's winds gusting at 270km (168 miles) per hour broke communication lines and rescuers were yet to reach hard-hit areas.

Lonsdale told AP he too has not been able to reach his family. "We do not know if our families are safe or not. As the leader of the nation, my whole heart is for the people, the nation," he said, adding that more than 90% of buildings in the capital, Port Vila, have been destroyed or damaged.

The president said his nation has witnessed first-hand the effects of climate change in recent years, suggesting it might have contributed to Cyclone Pam.

"Climate change is contributing to the disasters in Vanuatu. We see the level of sea rise. Change in weather patterns," he said. "This year we have heavy rain more than every year."

According to figures from the New Zealand Red Cross, 103,000 people have been affected by the storm. Vanuatu has a population of 267,000.