KUALA LUMPUR (Reuters) - The Sulu Sea between eastern Malaysia and the Philippines has become dangerous for merchant shipping due to rising threat of kidnappings, the International Maritime Bureau (IMB) said on Tuesday.

The Sulu archipelago is a stronghold of the Abu Sayyaf, an al-Qaeda linked group notorious for kidnappings and, increasingly, piracy.

The IMB report was released just hours after armed men attacked a fishing boat, killing eight fishermen, in what appeared to be a pirate attack off the southern Philippines.

IMB said global sea kidnappings rose three-fold in 2016, even as global piracy hit its lowest level in nearly 20 years. Pirates kidnapped 62 people for ransom in 15 separate incidents in 2016.

“The kidnapping of crew from ocean going merchant vessels in the Sulu Sea and their transfer to the Southern Philippines represents a notable escalation in attacks,” Kuala Lumpur-based IMB said.

IMB is advising charterers and owners to consider avoiding the Sulu Sea by routing vessels West of Kalimantan.

Tug boats, barges and fishing vessels have been targeted previously, but lately merchant ships are also being attacked, IMB said. They include the massive 180,000 tonne iron ore carrier Kumiai Shagang that saw an attempted attack late last year.

Several sailors and tourists were taken captive by Islamist militants last year in attacks on tug boats and yachts in the Celebes and Sulu seas, raising concern among defense officials from Indonesia, Malaysia and the Philippines.

In November, the Philippines agreed to allow Malaysia and Indonesia to carry out “hot pursuits” in its territorial waters, as the three nations looked to tackle kidnappings and piracy by Abu Sayyaf.

Commenting on the threat of kidnappings in the Sulu Sea area, one Singapore-based senior maritime security executive said: “The only worthwhile advice is to avoid the area.”