A powerful earthquake that struck near the sparsely populated Talaud Islands north of Indonesia's Sulawesi island has injured at least 49 people, officials said on Thursday.

Hundreds of buildings, including schools, churches and healthcare centres, were also damaged on the chain of islands that lie south of the Philippine island of Mindanao.

The U.S. Geological Survey put the quake that struck in the early hours of Thursday at a magnitude 7.2 and at a relatively shallow depth of 20 km (12.5 miles).

Indonesia's meteorology agency issued a tsunami warning, although it was later lifted.

A reporter for Indonesia's state radio station in the town of Tahuna said soon after the initial quake that frightened people had rushed out of their homes.

The big quake was followed by at least 20 aftershocks.

"At midday, there was a strong aftershock, everyone panicked and ran to higher ground, even patients being treated in hospital," Hutdam Manurat, a local government spokesman in the Talaud Islands, said by telephone.

Officials said they were still trying to assess damage in the scattered chain of islands lying on the edge of the Celebes Sea, with communications also severed in many areas.

The islands with a population of just over 80,000 that are part of North Sulawesi Province depend on agriculture and fishing.

The U.S. agency put the epicentre of the quake at 320 km north-northeast of Manado in Sulawesi and 280 km south-southeast of General Santos, on the island of Mindanao in the Philippines.

The Indonesian archipelago suffers frequent earthquakes, lying in an area of intense seismic activity where several tectonic plates collide.

A huge Indian Ocean tsunami in 2004 killed about 230,000 people across Asia, many of them in Indonesia.