(CNN) -- Pirates off Somalia have hijacked two more vesselsin the Gulf of Aden, the European Union naval force said Saturday --the third and fourth vessels they have captured this week.

The British-flagged Asian Glory was seized off Somalia late Friday, the naval force said. The nationality of the pirates was unclear, because the hijacking happened outside of the force's operations area, it said.
The British Foreign Office would not confirm the hijacking, but said no British nationals were aboard.
Also Friday, Somali pirates seized the Singaporean-flagged chemical tanker M/V Pramoni, also in the Gulf of Aden, the naval force said. The 20,000-ton chemical tanker was carrying a crew of 24 and was heading to Kandla, India, when attacked, the naval force said.
The crew consists of 17 Indonesians, five Chinese, one Nigerian and one Vietnamese, the naval force said. The ship's master reported all the crew were well after the hijacking, the naval force said.
The ship was heading toward Somalia after the hijacking, the naval force said.