Suspected Tamil Tiger rebels shot dead the commanding officer of Sri Lanka's military intelligence unit in Colombo on Tuesday.

A gunman riding a motorcycle pulled up alongside the vehicle of Major Nizam Mutalif, 39, and shot him dead at Colombo's Vijaya Kumaratunga road as he was driving to work, a military spokesman said.

Officials said they suspected Tiger rebels were behind the killing. The base their suspicions on the fact that Tiger rebels had accused the military intelligence of supporting a breakaway rebel faction.

Mutalif is the senior-most military officer to be killed since the ceasefire came into effect in February 2002.