Within 48 hours, the pirates seized the Lebanese-owned cargo ship MV Sea Horse, and the Greek-managed bulk carrier MV Irene E.M., whose 22 Filipino crew is believed to be safe. They also hijacked two Egyptian fishing boats.

Somali pirates have so far never executed hostages, but have sought to release ships in exchange for ransoms. Now, however, the bandits have pledged to retaliate for their five cohorts who were killed by U.S. and French forces in two separate hostage rescues over the weekend.

Three pirates were shot in a spectacular US military operation that rescued American Richard Phillips, captain of the Maersk Alabama, and two others were killed during the rescue of a French yacht.

Somali pirates currently hold more than a dozen ships

The latest releases and hijackings bring to at least 12 the number of ships being held by Somali pirates and to more than 200 the number of crewmen held hostage.

Among them is the German freighter Hansa Stavanger, a 20,000-ton container vessel that was hijacked on April 4 with five seamen from Germany and 19 from other nations. The German foreign ministry’s crisis squad is working toward their release.

While the German defense ministry does not believe the pirates will take revenge on the German hostages, senior official Thomas Kossendey told Deutschlandfunk German radio that the rescue operations have worsened the situation.

He warned that the fight against pirates in the region can only be successful if the international community takes steps to improve the political situation in Somalia, where nearly two decades of war and lawlessness have made piracy one of the few viable businesses.

The pirates’ relentless attacks have not only disrupted one of the world's busiest maritime trade routes; they have made international aid shipments for Somalia more difficult. According to the UN World Food Program in Geneva, about 90 percent of supplies are brought to the country by sea.