(Adds detail on casualties)

JAKARTA, Jan 23 (Reuters) - A strong earthquake struck Indonesia's Nias island west of Sumatra island, killing a child and injuring four people, officials said on Wednesday.

The magnitude 6.2 quake struck just after midnight, 172 km (107 miles) west of Sibolga at a depth of 12 km, the U.S. Geological Survey said in a bulletin on its Web site.

Health ministry official Rustam Pakaya said one child was killed in the quake after suffering a serious head injury and four people were hospitalised with injuries.

"The epicentre was on Nias island and caused panic, as well as cracking several houses," said Andri Gsetiaji at the meteorology agency in Jakarta.

A weaker aftershock later struck about 80 km southwest of Gunungsitoli, the capital of Nias, the official added.

Indonesia suffers frequent earthquakes since it lies on an area of intense seismic activity where a number of tectonic plates collide.

The Pacific Tsunami Warning Center said there were no immediate tsunami warnings or watches in effect.

In March 2005, a quake killed hundreds on Nias island, off the west coast of northern Sumatra. (Reporting by Telly Nathalia; Writing by Ed Davies; Editing by Matthew Jones and Alex Richardson)

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