Massive earthquakes hit the north Indian Ocean off Indonesia on Wednesday and triggered a tsunami watch. The tremors sent people scurrying from buildings as far away as southern India.

A tsunami alert was issued to countries all along the rim of the Indian Ocean, from Australia and India to as far off as Africa.

The U.S. Geological Survey said the first 8.6-magnitude quake was a shallow 22 km in the sea, 435 km from Aceh's provincial capital.

In India, tremors were felt almost all along the east coast, sending people running out of their homes and offices.

Tremors of varying intensity were felt in Tamil Nadu, Andhra Pradesh, Karnataka, Kerala and West Bengal, apart from the Andaman and Nicobar Islands, which are the closest to the epicentre.

In Chennai, tremors were felt in many areas, forcing closure of government offices, educational institutions and private companies. Traffic on the roads was chaotic.

In Indonesia, the first temblor of 8.6-magnitude struck at 2.08 p.m. It was followed by aftershocks with magnitudes ranging from 6.6 to 8.2.

Soon after the first quake, the Hyderabad-based Tsunami Warning Centre issued a tsunami alert for the coastal areas. With no sign of a tsunami emerging, the centre was almost on the verge of withdrawing the alert, when the second tremor occurred at 4.13 p.m. The alert was continued and ultimately it was withdrawn around 6 p.m.