A Malaysian oil tanker carrying 900,000 litres of diesel has been hijacked and taken into Indonesian waters, according to authorities in Malaysia.

The Malaysian Maritime Enforcement Agency (MMEA) said in a statement on Wednesday that the ship, Vier Harmoni, had been located in the waters off Batam, Indonesia.

The MMEA said they had yet to confirm the identity of the hijackers.

The ship had sailed from the Tanjung Pelepas port, in Malaysia, on Monday.

Al Jazeera's Step Vaessen, reporting from the Indonesian capital Jakarta, said it was unclear if the ship had been actually hijacked.

"Sources have told Al Jazeera that the crew may have taken the tanker to Indonesia," she said.

"Normally a piracy attack, which happens quite often in the Malacca Strait, follows a different pattern: strangers or pirates will enter the tanker carrying knives and machetes and will siphon off the oil in the middle of the sea and leave the tanker behind.

"It's a different story as far as we can tell at this stage."

Vaessen said the tanker was near the Indonesian island of Batam.

"But the Indonesian authorities are also confused about the situation and say they are in touch with the Malaysian maritime enforcement agency."

In June last year, pirates hijacked the Orkim Victory, a Malaysian tanker, and pumped the oil from it into another tanker before releasing it.

Source: Al Jazeera and agencies