The U.K.‘s Foreign Office (FCO) is advising against all but essential travel to Samoa, American Samoa and Tonga, a day after a series of earthquakes and a tsunami flattened villages, and swept people and cars out to sea.

According to the latest reports, more than 400 people have been killed as a result of the tsunami, which was triggered by an earthquake with a magnitude between 8.0 and 8.3.

Meanwhile rescuers have been struggling in heavy rain to find survivors in the rubble of collapsed buildings after a powerful quake on Indonesia’s island of Sumatra.

At least 200 people are known to have died in the 7.6 magnitude quake but the death toll is expected to rise dramatically.

In Indonesia, at least 450 are confirmed dead and thousands more missing or trapped in rubble after two earthquakes that hit less than 24 hours later. Officials have said the death toll on the island of Sumatra will “definitely” rise.

The first Indonesia earthquake, magnitude 7.6, struck at 10.16am GMT on Wednesday, some 55 miles under the sea north-west of the city of Padang. It was followed by a second tremor, magnitude 6.8, that hit at 1.52am GMT today about 150 miles further south-east.

Stephen Rogers, the British honorary consul in Samoa, confirmed that the entire island had been shaken by the initial earthquake.

He said: “It was a very big earthquake and the tsunami came about 20 to 30 minutes later. It took anything in its path. Roads have been pretty much washed away. Houses have been washed away or knocked down.”

Buildings were crushed and cars swept away from scores of villages.

Aid agencies are rushed to areas of western Indonesia, where the tremors have caused widespread landslides and at least two hospitals, mosques and hotels to collapse.

In Padang – home to nearly a million people – residents fought some fires with buckets of water and used their bare hands to search for survivors, pulling at the wreckage and tossing it away piece by piece.

Jusuf Kalla, vice-president of Indonesia, said the death toll was “definitely higher” than initial reports received by the government.

“It’s hard to tell because there is heavy rain and a blackout,” he said.

Siti Fadilah Supari, the country’s health minister, confirmed that two hospitals and a mall collapsed in Padang.

“This is a high-scale disaster, more powerful than the earthquake in Yogyakarta in 2006 when more than 3,000 people died,” the minister said, referring to a major city on the main Indonesian island of Java.

Stocks of emergency shelters, hygiene kits and clothing are ready to be distributed by aid teams funded by British charity Oxfam once workers can get through to the worst affected areas.

Padang lies on the same fault line as Indonesia’s Aceh province, which was devastated in the 2004 tsunami with 130,000 dead.

Experts are trying to determine whether the quake was linked to the one earlier in the South Pacific.