The vessel came under fire and was boarded by pirates on Sunday 250 miles (400 km) off the Somali coast. Spanish authorities have spoken to the kidnappers, who are demanding money, while the ship's captain said the crew was unharmed.
A source in the Spanish Ministry of Defense said a Spanish frigate is heading to the area with French and NATO ships also in the vicinity and available to take part in a possible hostage-release operation.
The Spanish and Kenyan embassies are said to be in contact with the pirates and using diplomatic means to try and secure their release.
On April 11, a crew of over 30 people on board a luxury French yacht was released after almost a week in the hands of Somali pirates.
Media said the crew was released without the use of force, but a French Navy frigate and a team of French commandos pursued and captured some of the suspected pirates, who will now face trial in France.
Earlier media reports said the Somali prime minister, Nur Hassan Hussein, had requested extra international assistance to combat piracy in the region.
Pirate attacks are a common occurrence off Somalia's coast, and in the past several vessels carrying United Nations aid to the country have been targeted. Attackers usually seize cargo, money and other valuables, but rarely capture ships or crew members.