"We can only pray that the pirates release the hostages. We are powerless to help," said Abdullahi Saed Yusuf, the district commissioner of Eyl.
The French foreign ministry said earlier that two French nationals were seized with the Venezuelan-registered boat.
French commandos carried out an operation in April and captured six pirates after a group of Somalis seized a French luxury sailing ship, Le Ponant, with its 30 crew, including 22 French nationals, and held them for a week.
Since the end of July, eight ships have been hijacked in the Gulf of Aden, including two Malaysian vessels as well as others from Germany, Iran and Japan.
The waters off Somalia are the most dangerous in the world for pirate attacks, with the International maritime bureau reporting 24 incidents in the area between April and June this year.