Seven Indonesian sailors have been taken hostage in the Sulu Sea in the southern Philippines, Indonesia's foreign minister said on Friday, the latest in a string of abductions in the waters between the two Southeast Asian neighbors.

"We got confirmation of an incident of kidnapping involving Indonesian crew of a ship," Indonesian Foreign Minister Retno Marsudi told reporters. He said the hijackings were carried out by two different armed groups.

Six of the 13 crew on board were freed, Marsudi said, and were on their way back to Indonesia.

The kidnappings come after the governments of Indonesia, the Philippines, and Malaysia agreed last month to carry out coordinated patrols to secure the region's busy waterways.

The Abu Sayyaf group in the southern Philippines is known to have seized hostages across the border and held them for ransom. This year it murdered two Canadian men when their ransoms were not paid.