Nairobi - Somali pirates have released the British-owned, Italian-operated Malaspina Castle and its mainly Bulgarian crew after a month of captivity, maritime officials said Sunday.

The 32,000-ton cargo ship was released on Saturday after an undisclosed ransom was paid, the Kenya-based East African Seafarers Assistance Programme said.

The Bulgarian government has confirmed the release and said that 24 crew members - 16 Bulgarians, four Filipinos ,two Ukrainians, a Russian and an Indian - were all safe.

Around 20 ships and several hundred seamen are still in the hands of pirates, who have been undeterred by the presence of 15 international warships in the region and several deadly rescue operations.

The International Maritime Bureau recorded over 100 successful and attempted acts of piracy in the Gulf of Aden and Indian Ocean near Somalia in the first quarter this year - a significant rise on the same period last year.