KINSHASA (Reuters) - A cargo plane carrying presidential staff crashed in eastern Congo on Thursday, and all eight passengers and crew are feared dead, a presidential adviser told Reuters on Friday.

The plane, carrying President Felix Tshisekedi’s driver, a logistics manager and some soldiers, was headed from Goma to the capital Kinshasa and went off radar on Thursday afternoon, an hour after departing, a statement from the civil aviation authority said.

The Russian embassy in Democratic Republic of Congo said on its Facebook page that preliminary information indicated that Russians were among the crew members on the Antonov jet.

Debris of the plane has been found, but the people aboard are still missing, said adviser Vidiye Tshimanga.

The cause of the accident was not yet clear.

Local media showed a crowd of hundreds of Tshisekedi supporters hitting the streets of Kinshasa after the news broke on Friday morning, fearing that the plane crash had been some kind of failed coup attempt against Tshisekedi. The president took over from long-standing former President Joseph Kabila this year.

No information immediately backed up such a claim. Kabila offered his condolences to Tshisekedi and all the victims, Kabila’s political coalition said in a Tweet.