Jakarta: An earthquake with a magnitude of 7.3 with a depth of 29 kilometres struck off the west coast of Indonesia's Northern Sumatra on Wednesday at 2:37 am, the US Geological Survey reported.

A tsunami warning has been issued by the Pacific Tsunami Warning Centre.

The quake, which had a depth of 29 kilometres, hit at 2:37 am (0007 IST) around 261 miles southwest of Banda Aceh.

An official at Indonesia's Meteorology and Geophysics Agency said it also had put out a tsunami alert, but that there were no immediate reports of casualties.

"The quake was in the sea and a tsunami warning is in force, but so far we have no reports of casualties or damage," Suharjono, the agency's technical chief.