Madrid - Spain's National Court has opened proceedings to determine whether it has the authority to try seven suspected Somali pirates who were captured by a Spanish vessel, judicial sources said Thursday.

MS Marques de Ensenada, which was participating in European Union patrols against pirates in the Indian Ocean, rescued and arrested the Somalis who had fallen into the water after their boat capsized when they were trying to enter a Panama-flagged vessel on Wednesday.

The Spaniards seized objects that could serve as evidence that the detainees were pirates, including their boat and a ladder, the sources said.

Judge Fernando Andreu was investigating whether the suspects could face trial in Spain, given that the incident occurred in international waters.