U.S. President Barack Obama pledged to fight piracy Monday but experts fear the killing of three Somali pirates during a rescue of a U.S. captain will spark aggressive reprisal attacks.

Capt. Richard Phillips was rescued Easter Sunday from a drifting lifeboat after U.S. Navy snipers shot and killed his three captors.

The pirates took the 53-year-old hostage late Wednesday during a failed hijacking of the U.S.-owned Maersk Alabama, which was carrying aid for people in Somalia, Rwanda and Uganda.

On Monday, Obama said his administration was resolved to "halt the rise of piracy" off the coast of Somalia.

"We're going to have to continue to work with our partners to prevent future attacks," Obama said at a news conference in Washington.

"We have to continue to be prepared to confront them when they arise, and we have to ensure that those who commit acts of piracy are held accountable for their crimes."

At present, some 230 foreign sailors are being held hostage in more than a dozen ships anchored in the region.

The pirates rarely harm the hostages, except in the case of a Taiwanese crew member who was killed under circumstances that remain unclear.

But Jamac Habeb, a 30-year-old self-proclaimed pirate, told The Associated Press that hostages will be killed in the future if necessary.

"From now on, if we capture foreign ships and their respective countries try to attack us, we will kill them," he said.

Abdullahi Lami, one of the pirates holding a Greek ship in the pirate den of Gaan, told AP that the pirates "will retaliate for the killings of our men."

Vice Adm. Bill Gortney, commander of U.S. Naval Forces Central Command, said the recent rescue "could escalate violence in this part of the world, no question about it."

Alan Bell, the president of security management consultancy firm Globe Risk Holdings, agreed that the recent incident changes the landscape in the region.

"It will change it because... they have three pirates that have been killed and they will do something to counter that," Bell told CTV's Canada AM on Monday.

Bell said authorities have not acted quick enough to deal with the pirate problem and it has now turned into a multi-million dollar business.

He said the pirates started out only robbing the ships but now they are taking passengers and boats hostage.

Meanwhile, the families of other hostages held by pirates are fearful.

The U.S. rescue operation "might be dangerous (for) the remaining hostages because the pirates might vent their anger on them," Vilma de Guzman, the wife of Filipino seafarer Ruel de Guzman, told The Associated Press.

Her husband has been held since Nov. 10 by pirates.

Noel Choong, of the IMB's piracy center in Kuala Lumpur, said there have been 74 attacks and 15 hijackings in 2009, compared to 111 attacks in all of 2008.

ABC's Dana Hughes, reporting from Mombasa, Kenya, said pirates made US$80 million by asking for ransom money last year.

"There are reports that there are people involved as far away as Dubai and Spain," she said.

Shane Murphy, second-in-command on the Maersk Alabama, urged Obama to act quickly.

"It's time for us to step in and put an end to this crisis," he said. "It's a crisis, wake up."

A fourth pirate, who was not on the lifeboat but participated in negotiations to free Phillips, is now in military custody.

Dean Boyd, a U.S. Justice Department spokesperson, said prosecutors are deciding whether to bring a case in the United States.

Somali pirates are relatively free to conduct such activity with little fear of retribution because Somalia has been without a central government since 1991.

Rebel factions have battled for control of the country since that time, and it is within that lawlessness that the pirates are able to operate.

It is believed that pirates have about 200 hostages currently hidden in Somalia.

With files from The Associated Press