Indonesia's foreign affairs ministry says seven seafarers kidnapped in the Philippines are safe and well.

Foreign minister Retno Marsudi told the Antara news agency: "We have maintained steady contact with several parties, both from Indonesia and the Philippines, since the kidnapping on June 24.

"Through constant coordination, we received information that the seven crew members of the tugboat are in good condition."

They were taken from a tug named Charles. Six other crew took the vessel into Semayang harbour in Balikpapan on 25 June after they were freed by the armed group.

Two groups of kidnappers took the men in separate incidents, but they are now thought to be held together, although almost constantly on the move.

It was the latest in a string of seizures involving seafarers from Indonesian tugs in the Philippines.