A plane carrying humanitarian aid with 17 people on board crashed into a mountain near Bukavu, in the east of the Democratic Republic of Congo, a United Nations source said on Sep. 2.

"The plane was found 15 kilometres (eight miles) northwest of Bukavu airport. There were 15 passengers and two crew on board," said the spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA) in Kinshasa, Christophe Illemassene.

The US-based company which contracted the plane, Air Serv, said in a statement there were "no known survivors".

The company provides air transport for the international humanitarian community.

The plane has been found on a steep ridge eight miles (15 kilometres) northwest of Bukavu, it said.

"The aircraft was piloted by two crew members and carried 15 passengers. Ariel survey by helicopter indicates that there are no known survivors," it said.

The plane was reported missing late on Sep. 1 after it failed to land as scheduled at Bukavu, provincial capital of South Kivu.

The circumstances of the accident are still unknown. The weather was reported to have been particularly bad in the mountainous South Kivu region on Sep. 1, UN sources said.

Financed by international donors, Air Serv normally carries humanitarian aid workers throughout the DRC. It also operates in Chad, Uganda, Mozambique, Iraq and Afghanistan.

Air accidents are relatively frequent in the DRC. On Apr. 15, a DC-9 operated by a Congolese company crashed near Goma, killing at least 47 people and injuring more than 100.

All Congolese carriers are on a European Union blacklist banning them from operating in EU airspace over safety concerns.