The Indonesian Business Competition Supervisory Commission (KPPU) had said in February that its tribunal ruled that AHM and PT Yamaha Indonesia had agreed to set prices for 110-120 cc automatic scooters.

The tribunal set a 25 billion rupiah ($1.85 million) fine for Yamaha Indonesia and a 22.5 billion rupiah fine for AHM.

AHM is a motorbike distributor jointly owned by Indonesian conglomerate PT Astra International and Japan's Honda Motor Co Ltd. Yamaha Indonesia is part of Japan's Yamaha Group.

Motorbikes are hugely popular in Southeast Asia's biggest economy and their sales are a key indicator of consumption.

Last year, the two companies controlled 97.4 percent of Indonesia's motorbike market.

The companies appealed the tribunal's decision in a Jakarta court, but the ruling on Monday upheld the KPPU's decision.

"This ruling is disappointing for us, thus we will continue to seek justice because we reject the accusation by KPPU," Ahmad Muhibbuddin, an AHM spokesman, said in a statement. Muhibbuddin said AHM will file an appeal to the Supreme Court.

A Yamaha Indonesia spokesman also said it would appeal but did not provide details.