INTRO: Sri Lankan military on alert as Tamil Tiger rebels launch air raid.
STORY: Sri Lanka(斯里蘭卡)'s military went on alert on Sunday (April 29) when radar detected a suspect plane, military sources said, and witnesses said they heard explosions and firing in the capital Colombo(科倫坡：可倫坡).
A Reuters correspondent at Colombo international airport said passengers had been told to get off their flights, but were later told to re-embark. The security alert came after a similar one late on Thursday (April 26) when Sri Lankan authorities temporarily closed Colombo international airport after reports suspicious airplanes were seen flying south along the coast.
That air raid scare came two days after the Tamil Tiger rebels(泰米爾猛虎組織：塔米爾之虎反叛軍)' newly unveiled air wing staged its second attack ever, dropping bombs on a military position in the north killing six people.
The rebels' first air strike was on the air force base next to Colombo airport, and it took the military by surprise. Analysts believe the Tamil Tigers' air force consists of just two to five light propeller planes assembled from pieces smuggled in over time.
The Liberation Tigers of Tamil Eelam(泰米爾民族解放之虎), as the rebels are officially known, want to create an independent state in the north and east of the island for ethnic minority Tamils.
Since 1983, the war in Sri Lanka has claimed some 68,000 lives, including more than 4,000 since late 2005. The intensified violence of the past 16 months has left a 2002 ceasefire in tatters.