A TSUNAMI watch has been issued for countries across the Indian Ocean after a large earthquake hit waters off Indonesia, sending people pouring from their homes in panic.

The US Geological Survey said the 8.7-magnitude quake was centred 20 miles beneath the ocean floor around 270 miles from Aceh’s provincial capital.

A giant 9.1-magnitude quake off the country on Boxing Day 2004, triggered a tsunami in the Indian Ocean that killed 230,000 people, nearly three quarters of them in Aceh.

The Pacific Tsunami Warning Centre in Hawaii said a tsunami watch was in effect for Indonesia, India, Sri Lanka, Australia, Myanmar, Thailand, the Maldives and other Indian Ocean islands, Malaysia, Pakistan, Somalia, Oman, Iran, Bangladesh, Kenya, South Africa and Singapore.

A tsunami watch means there is the potential for a tsunami, not that one is imminent.

David Cameron today pledged Britain’s support to Indonesia today in the wake of an earthquake off Aceh province as he visited the country.

Speaking at a joint press conference with the Indonesian President in Jakarta, the Prime Minister said Britain “stood ready” to help in any way necessary.

He arrived in Indonesia this morning but reports suggest the 8.9 magnitude earthquake was not felt in the capital.

Mr Cameron said said he was “hugely concerned” by news of the quake, telling Susilo Bambang Yudhoyono: “Our thoughts should be with those who are affected.

“Britain of course stands ready to help if help is required.

“We will stand with you and your government and your people at this time of worry.”

Mr Yudhoyono moved to calm nerves, saying that there appeared to be no serious casualties and local residents had been taken to safety.

He added that “as of this time there is no threat of tsunami” - despite an international warning being issued.

Meanwhile Thailand’s National Disaster Warning Centre issued an evacuation order to residents in six provinces along the country’s west coast, including the popular tourist destinations of Phuket, Krabi and Phang-Nga.

Indonesia’s Meteorology and Geophysics Agency said a warning had been issued for cities all along the coast of Sumatra island.

The tremor was felt in Singapore, Thailand, Bangladesh, Malaysia and India. High-rise apartments and offices on Malaysia’s west coast shook for at least a minute.

People in Banda Aceh screamed as they jumped into cars and on the backs of motorcycles, clogging streets as they fled to high ground.

Indonesia straddles a series of fault lines that makes the vast island nation prone to volcanic and seismic activity.