U.N. chief Ban Ki-moon is calling for coordinated action against pirates who pose an increasing threat to shipping in the Gulf of Guinea.

The secretary-general spoke Wednesday at a U.N. Security Council meeting called to discuss piracy in the gulf, located off the southern coast of west Africa.

Pirates have attacked about 20 ships in the area this year, and the International Maritime Bureau has posted warnings for vessels traveling near Nigeria, Benin, Guinea, and Cameroon.

Mr. Ban urged regional groups, like the Economic Community of West African States, to develop a comprehensive strategy against pirates. He noted that Benin and Nigeria recently launched joint patrols to monitor the waters off Benin.

The U.N. chief also said he will send a team of U.N. officials to the region next month to assess the situation.

Pirates in the Gulf of Guinea operate on a smaller scale than pirates in Somalia but have hijacked several ships this year.

Experts have noted that West African pirates tend to attack ships for their cargo, while Somali pirates usually hold ships and crews for ransom.