US forces are searching for a missing American reconnaissance team four days after a special forces helicopter sent in to extract them was shot down in Afghanistan. 

'We have not located them as of yet, but we are doing active patrolling to find our missing US service members,' US military spokesman Lieutenant Colonel Jerry O'Hara said.

He did not say how many troops were in the team.  

Sixteen personnel, including eight elite US Navy Seals, were killed when an MH-47 Chinook helicopter was downed by a rocket propelled grenade fired by militants in eastern Kunar province on Tuesday.