The Danish Navy says it has freed 16 hostages held by Somali pirates, but two other hostages were apparently killed during the rescue operation.

The warship Absalon fired on and intercepted a pirate mother ship as it tried to sneak away from the Somali coast Monday, according to a Danish Navy statement.

It says Absalon crew members boarded the ship and found 17 suspected pirates along with 18 hostages from the ship's original crew.  It says two of the hostages were found badly injured and died, despite medical attention.

The statement said it is not clear how the hostages died, and an investigation is underway.

Warships from several countries patrol waters near Somalia in an effort to stop pirates from hijacking vessels that pass through the Gulf of Aden and northern Indian Ocean.

Somali pirates have made hundreds of millions of dollars in ransom by seizing ships in recent years.

The number of successful hijackings has dropped sharply during the past six months.  Analysts credit the trend mainly to ships taking better security measures, such as keeping armed guards on board.