Indonesia protested on Friday that the Malaysian navy intervened to stop the arrest of Malaysian fishermen suspected of poaching in Indonesian waters.

Malaysian embassy officials in Jakarta were summoned to explain the incident to the Indonesian government, which demanded the fishermen be handed over and an investigation.

"We have summoned them. We demand that this incident be investigated," foreign ministry spokesman Yuri Thamrin told a press conference.

Indonesia says a Malaysian navy ship foiled the arrest Wednesday of Malaysian fishermen accused of poaching off the northern coast of Sumatra island.

Marine police squad director Brigadier General N Sutisna was quoted by the Jakarta Post as saying that the navy ship entered Indonesian waters and forced his officers to release the alleged poachers "at gunpoint".

"We let go of the fish poachers as we were forced at gunpoint by the Malaysia seamen. They intimidated us and made our officers go aboard the Malaysian naval ship," Sutisna said.

The two countries have been at loggerheads due to overlapping claims on an oil-rich maritime area east of Borneo island. The dispute began when Malaysia granted an oil concession in February to Anglo-Dutch firm Shell.

Both countries deployed warships to the region, where tensions reached a peak in April as vessels from both nations brushed sides in the disputed area. Officials from both sides began negotiations in March to settle the claims.