The plan to send 48 orang-utans confiscated from a private zoo back to Indonesia faces a week-long delay because the plane due to transport them is unable to land in Thailand after the coup.

The Ministry of Natural Resources and Environment had planned to send the apes, confiscated from the private Safari World tourist park near Bangkok, to Indonesia tomorrow.

But the orang-utans are now due to be flown back next Friday on board an Indonesian navy cargo plane.

"Indonesia should be understanding," said Schwann Tunhikorn, deputy director-general of the National Park, Wildlife and Plant Conservation Department, which is finally sending the apes back - three years after they were confiscated.

The orang-utans are set to get a VIP welcome when they return to Indonesia, with the wife of President Susilo Bambang Yudhoyono reportedly ready to welcome them after they arrive in Jakarta.

They will then be flown to a well-known orang-utan centre in northern Borneo.

However, the return of the smuggled apes continues to be mired in argument and controversy. Indonesian officials and the representative of an animal welfare group acting for them in Thailand had hoped another five orang-utans taken from Safari World and now at the Night Safari park in Chiang Mai would also be returned.

Edwin Wiek, of the Borneo Orang-utan Survival Foundation, said: "The Night Safari is refusing to return these five animals, which were also smuggled into Thailand and also belong to Indonesia."

Wiek accused the Chiang Mai park of mistreating the five apes, which have officially been "borrowed from the department".

He said the orang-utans were being kept in a narrow, hot place and not being cared for well enough. They have been used to draw tourists who pay to have their pictures taken with the apes.

"If the department does not take the five orang-utans back to Indonesia, it could be regarded as an act of embezzlement," Wiek said.

The 48 apes due to be returned are now at a wildlife centre in Ratchaburi. Seven of them reportedly have Hepatitis B.

Former Natural Resources and Environment Minister Yongyuth Tiyapairat had planned to go to Jakarta for the return of the orang-utans, but he was detained yesterday after surrendering to the Army Command in Bangkok.