Update 4: Friend at Suntec just felt a second tremor lasting about 15 seconds.
Update 3: CNN has more news here.
Update 2: Ministry of Home Affairs recommends these safety tips.
Update 1: An earthquake was detected at 11:49am, 6 Mar 2007 in CENTRAL SUMATRA, approximately 430km from Singapore. The magnitude of the earthquake is 6.6 on the Richter scale. The epicentre is located at latitude 0.4 South and longitude 100.4 East.
USGS reports it as a 6.3.
From my buddy in Suntec:
"wahrow, suntec building just swayed for about 10secs"
"10% in me scared that its circle line.. but think its more earthquake in sumatra"
Friends are reporting tremors in Sengkang too. Around 11.55am. We felt it here briefly in Katong too.
Wife just called from Beach Road and said her colleagues and many from her building (Shaw Tower) have evacuated and are waiting on the first floor. She said the tremors lasted quite long and they felt it quite a bit. Made her giddy.
Friend in Suntec is now evacuating too, because his boss says, just in case.
In other news, Channel NewsAsia's website is the first casualty of the tremors.
I will update more when I get news.