A very strong earthquake of 7.7 magnitude struck near India's Nicobar Islands and northwest of the tip of Indonesia's Sumatra island on Saturday, the U.S. Geological Survey said.

A regional tsunami watch was in effect for all areas of the Indian Ocean, the Pacific Tsunami Warning Center said on its website. The epicenter of the quake was 107 miles (171 km) west of Misha on the Nicobar Islands at a depth of 20.5 miles (33 km), USGS said. [ ALERT NET ]