Defence Minister Pieter De Crem told reporters in Brussels that 10 pirates had abandoned the ship early on Sunday, a day after a plane dropped the ransom cash into the sea near the Pompei, reported AP news agency.
Belgian officials said the money had been paid by the insurance company of the ship, and that the goverment had provided assistance in the long drawn-out negotiations.
The director of the Belgian government's crisis centre, Jaak Rase told the BBC: "This was the only way to free and to put an end to this hijacking."
He added:"About 160 contacts we had by telephone, and all the time there were discussions about the ransom."
The release of the Pompei brings the number of ships still held by pirates down to 12, with a total of some 200 crew, according to the International Maritime Bureau.
Last week, a Dutch cargo ship was released after being held by Somali pirates since early May. One Ukrainian sailor was shot dead and eight other crew members injured.
Earlier this month, EU ministers agreed to extend an anti-piracy operation - known as Atalanta - off the Horn of Africa until the end of 2010.
Two dozen ships from European Union nations, including Britain, France, Germany and Italy, patrol an area of about two million square miles.
Operation Atalanta's new commander, Rear Adm Peter Hudson, told the BBC last week that successful pirate attacks had fallen in the past six months, but said a "full solution" lay ashore, not at sea.
He said the key was to bring stability to Somalia, which has been without a stable government since 1991.
When first loaded, the map's focus falls on Somalia where most of the pirates are based. Use the arrow icons to scroll left towards Europe and the United States which are both playing a central role in tackling the problem.
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