NAIROBI - Somali pirates captured a freighter, a bulk carrier and a chemical tanker in a few days, defying foreign warships in the Gulf of Aden and ending the year with a flurry after collecting millions in ransom.

The marauding sea bandits' latest catch was the St James Park, a UK-flagged chemical tanker with a crew of 26 from nine different countries, Andrew Mwangura of the East Africa Seafarers Assistance Program said Tuesday.

He said the vessel, which was seized on Monday en route from Spain to Thailand, had been commandeered near the northern Somali coast.

"It is expected to arrive there later this evening," Mwangura told AFP.

He said the vessel's last port of call was Jeddah in Saudi Arabia and that the crew included seamen from Russia, Ukraine, Bulgaria, Romania, Philippines, Poland, Georgia, India and Turkey.

Also on Monday, Somali pirates captured a Greek-flagged bulk carrier transporting fertilizer, Mwangura said.

The 52,000-ton Navios Apollon was hijacked "en route from Tampa, Florida to Rozy, India," with a crew consisting of a Greek captain and 18 Filipinos.

The ship was boarded by 10 men on speedboats in the Indian Ocean northeast of the Seychelles archipelago, according to the Greek coastguard.

Earlier, pirates seized a Yemeni freighter and 15 crew members.

The Al-Mahmoudia2 left the port of Aden, in Yemen, on December 18, the Yemeni authorities said on Monday, without revealing the nature of its cargo or destination.

Crucially, the Yemeni freighter and the UK-flagged chemical tanker was intercepted by pirates in the Gulf of Aden, a key maritime bottleneck near the entrance to the Red Sea.

The two attacks in the Gulf of Aden were the first since August and came as international naval missions were trumpeting the results of a year-long effort to secure the area.

Since the end of the summer monsoon season allowed pirate attacks to resume three months ago, Somali pirates had abandoned the Gulf of Aden for the wide open seas of the Indian Ocean, venturing as far as the Seychelles and beyond.

Despite the increased international presence off Somalia's coastline -- the longest in Africa -- pirates raked in huge ransoms.

On Sunday, pirates said they collected US$3.5 million for the release of the Chinese bulk carrier Dexinhai.

The Singapore-flagged MV Kota Wajar was also released nearly 10 weeks after being hijacked, the European Union naval task force said Monday. The amount of the ransom is not yet known.

The latest captures and releases bring to at least 11 the number of ships currently held by pirates, together with close to 250 seamen, according to Ecoterra International, an environmentalist NGO monitoring maritime activity in the region.

Among those in captivity is a British couple captured on October 22 while sailing their yacht to Tanzania.

In a recent video broadcast, the pair -- Paul and Rachel Chandler -- said that their captors were "losing patience" and could kill them within a week if no ransom was paid.

The couple was briefly held on board the recently-released MV Kota Wajar.

Alongside the EU, the United States, NATO and other national navies also deployed warships off the Somali coast in December 2008 to protect vessels and secure maritime routes in the Gulf of Aden and the Indian Ocean.

Thanks to state-of-the-art technology, huge budgets and ever-improving coordination, the foreign armada has thwarted many attacks and captured dozens of pirates, generally equipped with rudimentary skiffs, ladders and grapnels.

But one out of four ships sailing through the danger zone still does not comply with international recommendations for safe passage, the navies say.

Observers say piracy can only be eradicated through onshore efforts to end Somalia's 18 years of near-daily violence and lawlessness that have made the phenomenon one of the few viable businesses.