CAIRO (Reuters) - Egyptian navy forces seized a ship carrying heavy weapons as it entered Egyptian territorial waters in the Red Sea late on Wednesday, three security sources told Reuters on Thursday.

The ship, with a crew of at least seven, spent a week in international waters before entering Egyptian waters, the sources said. They gave no details of the origin, nationality or destination of the vessel.

The ship was escorted into the port of Safaga, 569 km (356 miles) southeast of Cairo, where the crew members are being interrogated and an investigation is ongoing to determine whether the weapons are legal, the sources said.

The Egyptian Navy declined official comment on the incident.

(Reporting by Asma Alsharif; Editing by Paul Taylor and Robin Pomeroy)