Somali pirates attacked two new ships off the Horn of Africa Saturday.
In one assault, a NATO commander said pirates captured a Belgian vessel, the Pompei, traveling south to the Seychelles islands.
The ship was carrying 10 crew members, including two Belgians, four Croatians and three Filipinos. Belgian officials said the ship had sent out two distress signals.
Further north, in the Gulf of Aden, the NATO commander said forces responded to a distress signal sent out by a Marshall Islands-flagged tanker that also came under attack.
He said the Dutch forces responding to the call caught up with the pirates responsible and ended up rescuing 20 Yemeni hostages being held on another vessel, which the pirates had been using as their "mother ship."
The commander said the Dutch forces chased the pirates to the hijacked Yemeni fishing dhow after spotting them fleeing on a skiff.
In addition to rescuing the 20 fisherman, who had been held for about a week, the forces also briefly detained seven pirates.
On Friday, American ship captain Richard Phillips returned home, five days after a U.S. Navy operation freed him from pirates in the same area.
Phillips' vessel was attacked April 8 as it sailed off the coast of the northern Puntland region of Somalia.
Nearly a dozen countries are running naval patrols off Somalia to combat pirates who have hijacked some 60 ships since the start of 2008.
Some information for this report was provided by AP and Reuters.