Somali pirates attacked two more vessels on Saturday in the Indian Ocean off the Horn of Africa country, seizing a Belgian dredger but thwarted in an attempt to hold a tanker, according to reports monitored.

This photo taken on April 18, 2009 shows a print page of the undated photo of the missing Belgian dredger "Pompei" in Brussels, capital of Belgium. A Belgian dredger with 10 crew members on board was suspected of having been hijacked by pirates off the Somali coast on Saturday morning.(Xinhua Photo)

A Belgian dredger with 10 crew members on board was hijacked by pirates on Saturday morning, Belgian broadcaster VRT said.

The ship, which is owned by Belgian dredging firms Jan De Nul and DEME, was reportedly missing off the Somali coast. It sounded a silent alarm twice early in the morning, a staff member of the Belgian government's crisis center told the VRT.

Jaak Raes of the crisis center, which is monitoring the situation, said the crew on board the Pompei include two Belgians, one Dutchman and several Croatian and Filipino nationals.

The Pompei first sounded the alarm at around 5:30 a.m. A second distress call was received by coast guards at around 6 a.m.

Later in the day, NATO forces captured seven Somali pirates in the Gulf of Aden and freed 20 people taken hostages.

A NATO spokesperson said a Dutch warship with NATO mission took actions after the pirates launched an attack on the tanker MTHandytankers Magic.

They chased the pirates fleeing on a small skiff before capturing a Yemeni-flagged fishing dhow taken by the pirates on Sunday as their "mother ship". The Dutch forces freed 20 Yemeni hostages on the dhow.

The incident took place after a U.S. captain who has been held hostage by Somali pirate for five days arrived on Friday at his hometown in Vermont.

After a five-day standoff, the U.S. Navy SEALs killed the three pirates holding Phillips hostage in a lifeboat, and set him free.

Despite an international flotilla, Somali pirates have attacked at least 80 vessels this year, holding at least 16 ships and more than 250 crew members. After a brief lull apparently balking at the increasing presence of foreign warships against piracy, they made a comeback recently extending their attacks to a much larger area in the Indian Ocean, as far as off the Seychelles islands.

For almost two decades, Somalia have been in anarchy since its government was toppled by warlords in 1991, with its people living in chaos and poverty. A transitional government established in 2000 has been too weak to combat piracy stemming from the war-torn soil.

(Xinhua News Agency April 19, 2009)