A Spanish tuna fishing boat carrying a crew of 26 was seized on Sunday by pirates off the Somali coast, Spain's foreign ministry said, adding no one was injured in the attack.
The Playa de Bakio "was boarded and apparently seized while it was fishing in Somali waters" at 1:00 pm (1100 GMT), the ministry said in a statement.
Thirteen of the crew are Spanish nationals, it said, while Spanish media reported that their remaining 13 crewmates are African nationals.
Four pirates armed with grenade launchers seized the boat, which is based in the Basque town of Bremeo, some 400 kilometres (250 miles) off the coast of Somalia, Basque government officials told the Europa Press news agency.
The ship was damaged in the attack but it is still able to sail and it appears to be headed towards land, they added.
"The defence ministry has instructed one of its ships which is nearby to head immediately to the area of the incident," the foreign ministry's statement said.
A Spanish military frigate that was in the Red Sea was heading towards the are where the fishing boat was seized, a government source said.
The defence ministry has also been in contact with military officials of nations with a military presence in the area to request "logistics support and help in locating the affected boat, the statement added.
The seizure comes two days after a Paris court charged six Somalis with taking a the crew of the French luxury yacht Le Ponant hostage earlier this month.
The six were captured by French special forces, along with 200,000 dollars (125,000 euros) of suspected ransom money, after they released the 30-strong crew of the yacht on April 11 after holding the group hostage for a week off the coast of the self-proclaimed autonomous region of Puntland.
The Spanish fishing boat was seized in the same area where the French yacht was attacked, RNE added.
Earlier this month French Prime Minister Francois Fillon called on the United Nations to launch an "international initiative" to protect maritime shipping in areas where piracy is on the rise, such as off Somalia.
The coastal waters of Somalia, which has not had an effective central government for more than 17 years and is plagued by insecurity, are considered to be among the most hazardous in the world.
Last year more than 25 ships were seized by pirates in Somali coastal waters despite US navy patrols.
The International Maritime Bureau advises merchant ships to stay at least 200 nautical miles from the Somali coast because of the risk of piracy.