Jakarta (ANTARA News) - A 6.4-magnitude quake struck off the west coast of Indonesia's Sumatra island on Tuesday, briefly triggering a tsunami alert and sending people running from their homes, officials said.The quake struck at 10:43 am (0343 GMT), 160 kilometres (100 miles) northwest of the town of Lais at a depth of 20 kilometres, the meteorology agency said.It rattled the same area hit by a massive 8.4-magnitude quake and a multitude of aftershocks last month that left 23 people dead. At least two others also died in the aftermath on a remote set of islands due to the slow arrival of medical aid.The meteorology agency warned a tsunami could strike after the morning quake but lifted its alert about an hour later.The US Geological Survey put the quake's magnitude at 5.7.A policeman from Bengkulu told AFP that no reports of damage had been received and that aftershocks were becoming "a usual thing for us." "The tremor was quite strong and lasted about half a minute -- some people ran out of their houses," Salamun Haris, an official in North Bengkulu district where Lais is located, told ElShinta radio."After the last major quake, we called for people especially around North Bengkulu to be aware but not to panic," he said."So far there is no information about any damage, but most houses are already cracked so maybe this made them worse." Resident Lizar al-Fansi in nearby Bengkulu told AFP that the quake felt similar in strength to the other aftershocks that have shaken the area since the massive September 12 quake."Everybody has rushed out of buildings," she said.Tsunami alerts here are issued based on the likelihood of waves striking rather than due to a detected change in sea levels.Indonesia sits on the so-called Pacific Ring of Fire, where continental plates meet -- and where earthquakes are a regular and often deadly occurrence.Some 168,000 people were killed in Aceh, the province at the tip of Sumatra island, when a massive quake and tsunami lashed countries around the Indian Ocean in December 2004. Indonesia was the country worst affected.A nationwide tsunami warning system is still being installed across the archipelago.Some 180 seismic sensors are to be built along with 10 warning centres. So far 73 sensors are operational and the full system is expected to be complete by the end of next year. (*)

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