Somali pirates have released a chemical tanker, the Stolt Valor, after they received a $1.1 million ransom, a regional maritime official said.

Two other ships could be released before Nov 25 because negotiations between the owners and pirates had been going well, said Andrew Mwangura, director of the East African Seafarers' Assistance Programme that monitors piracy.

But he said the pirates, who have made shipping routes off Somalia among the most dangerous in the world, had seized another ship, a Japanese cargo vessel.

'It (the Stolt Valor) was released last night and after release, another ship was taken, a Japanese one with South Korean connections,' Mwangura told Reuters, adding that a $1.1 million ransom had been paid for the Stolt Valor.

'Stolt Valor is among three ships that are to be released this month,' he added, naming them as the MV Genius and the MV Action but without giving further details.

The pirates off the dangerous Somali coast have taken three ships within the past week alone; another chemical tanker chartered by chemical tanker shipping group Stolt-Nielsen, a Chinese fishing vessel and a Turkish tanker.

The Japanese cargo ship hijacked late on Saturday was carrying 23 sailors including five South Koreans, according to South Korea's Yonhap news agency.

Piracy off Somalia has plagued the shipping lane linking the Middle East Gulf and Asia to Europe and beyond via the Suez Canal and increased insurance premiums.

The International Maritime Bureau says 199 incidents of piracy or attempted piracy were reported worldwide from January to September this year, of which 63 were in the Gulf of Aden and off the Somali coast. - Reuters