The Russian-made MI-171 helicopter crashed about a quarter of an hour after takeoff in a residential area on the fringes of Hanoi, some 30 kilometers (19 miles) from the city center, according to Vietnamese officials.

Medical and military sources said 16 people were killed, while five others were being treated for serious burn injuries, according to a doctor at a military hospital.

Reports in the state-controlled media said most of the 21 people on board were paratrooper recruits. There were also two trainers and three crew members on board.

Officials did not say whether any civilians had been hurt or killed.

Most of Vietnam's military helicopters are Soviet-era models from the country's Cold War ally, Russia. The MI-171 is mostly used for transport, but there are gunship models.

tj/pfd (AP, Reuters, AFP)