TAIPEI – An eight-year-old girl has died after being swept out to sea off Taiwan as Typhoon Soudelor claimed its first human lie in its march across the northwestern Pacific.

Another young girl is missing in the same incident.

Soudelor, billed as the biggest typhoon of the year, has forced thousands of people to flee and troops to be placed on standby.

The United States National Weather Service in Guam has admitted that it did not expect Typhoon Soudelor to be as strong as it was when it hit the Northern Marianas on Sunday.

The typhoon destroyed more than 380 homes and damaged other infrastructure on the territory’s main island of Saipan.

The service has acknowledged that its wind forecasts were too low, affirming residents’ suspicion that the devastating winds were much stronger than forecast.

US President Barack Obama has signed a major disaster declaration for the Northern Marianas. It will free up federal funds to help meet immediate emergency needs.

In his request for disaster declaration, the acting governor Ralph Torres puts the damage to the CNMI from the typhoon at $US20 milllion dollars.

On the island of Taiwan to the west, authorities have warned that Typhoon Soudelor may strengthen before making landfall.

“The girl who died and the one who went missing were swept away by strong waves,” a spokesman for the National Fire Agency told AFP.

Another child was also missing in the same incident, while a 38-year-old woman and another girl survived.

More than 2000 people have already been relocated from Taiwan’s outlying islands, popular with tourists, and troops were preparing to help more residents move from their homes into shelters.

The storm is set to make a direct hit on the east coast, though much of the island will be lashed by torrential rain.

Packing maximum wind speeds of 173 kilometres per hour near its centre, Soudelor was 370 kilometres south-east of eastern Hualien county Friday afternoon.

It was due to make landfall on the central east coast late Friday or early Saturday morning.

Currently described as a “moderate typhoon” by Taiwan’s Central Weather Bureau – the second highest category – it could be raised to the top category of “severe typhoon” if wind speeds near the centre reach more than 184 kilometres an hour.

“We don’t rule out the chances Soudelor could strengthen later,” the weather bureau said.

Soudelor was described as a “super typhoon” by the Hong Kong Observatory earlier in the week as it reached maximum sustained wind speeds of 230 kilometres an hour.

The storm will unleash heavy rains across northern and eastern Taiwan between Friday night and Saturday. Both land and sea warnings have been raised.

The defence ministry said it had readied 100 shelters that could accommodate more than 45,000 people while around 35,000 soldiers were placed on standby for disaster relief.