The injured men, along with eight other navy personnel, were being flown back to their ship in the Lincoln battle group on Monday, said Captain Joe Plenzler, a US military spokesman in Medan, 400km southeast of Banda Aceh. 

The US military suspended helicopter flights for about two hours after the crash. "Typically what happens whenever there is an event with an aircraft, they will suspend flight operations and start an investigation," Plenzler said.

"It gives them time to pause and take a look at the safety situation. But they have since resumed flying." 

No foul play

The SH60 helicopter crashed in a rice paddy about 500m from the airport in Banda Aceh, the main city on Indonesia's tsunami-battered Sumatra island, as it was trying to land, he said. 

"We can rule out ground fire"

Captain Joe Plenzler,
US military spokesman

"There was no fire ball but a little smoke. It landed on its side," Plenzler said, adding that the helicopter's propeller was twisted from the impact of the crash. 

US authorities said there was no indication the helicopter had been shot down. 

"We can rule out ground fire, but until there is investigation the determination of the cause of the accident can't be made," Plenzler said. 

Airport still functioning

There was a shooting incident close to a United Nations compound in Banda Aceh on Sunday that local police blamed on separatist rebels who operate in the area.

Nobody was injured and aid officials said they did not believe relief workers were targeted. 

The authorities quickly cordoned off the area near the helicopter crash on Monday and US officials began searching the field around the crash site, apparently for debris.

The airport at Banda Aceh "is still functioning and the crash shouldn't effect relief operations", said Plenzler. 

The helicopter was flying in personnel to the airport from the USS Abraham Lincoln group off the coast of Sumatra, he said.