SINGAPORE (Reuters) - An earthquake of magnitude 6.6 struck south of the Indonesian town of Raba, off the central island of Sumbawa, the U.S. Geological Survey said, the second quake to hit the area on Tuesday.

There was no immediate tsunami warning or reports of damage or casualties from the quake, which hit at a depth of 36 km (22 miles), at a distance of about 230 km (143 miles) south of Raba in the east of the island, which forms part of West Nusa Tenggara province.

The quake followed one of magnitude 6 that struck in the same area.