COLOMBO - At least nine people were slightly hurt as a small explosion took place in Sri Lankan capital Colombo Thursday morning, said the military.

Military spokesman Prasad Samarasinghe said the explosion happened when a small hand grenade was thrown to a group of people at around 6:45 am (0115 GMT) at Colombo's business district of Fort.

Samarasinghe said he believed it is a private matter.

Earlier, the police said business rivalry is being suspected behind the explosion.  

The Sri Lankan capital remained largely free of explosion after the defeat of Tamil Tiger rebels in May 2009.