Air and sea rescue services are out in force in the hunt for a Dutch fishing boat which issued an emergency signal in the early hours of Thursday morning.

The boat, based at the Urk fishing port, was in action west of the Wadden Island of Texel when the automated alarm was sent out. The alarm is only activated when it comes in contact with water.

The boat was fishing for shrimp and had two crew on board, including its owner. Both are experienced fishermen.

Other fishing boats and a minesweeper from the Den Helder navy base are also involved in the search operation.

Helicopters have spotted an empty life raft and life jacket at sea, broadcaster NOS said.