Nairobi/Washington - US President Barack Obama on Monday praised the rescue of a US captain from the clutches of Somali pirates in a dramatic Navy operation and said the US would work to halt piracy in the region.

US Navy snipers on Sunday shot dead three Somali pirates who had been holding captain Richard Phillips in a lifeboat since Wednesday, following a failed attempt to seize the his ship the Maersk Alabama.

"I share our nation's admiration for Captain Phillips' courage, and leadership, and selfless concern for his crew," Obama said, also praising military efforts to rescue the captain.

"I want to be very clear that we are resolved to halt the rise of piracy in that region. And to achieve that goal, we're going to have to continue to work with our partners to prevent future attacks," Obama said. "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."

Crew members of the Maersk Alabama paid tribute to their captain earlier Monday and called on Obama to tackle piracy off the coast of Somalia.

A fourth pirate - who was on a US Navy ship, the USS Bainbridge, to negotiate Phillips' release at the time of the shooting - is in custody.

Captain Phillips has played down his part in the drama, instead praising the Navy Seals that freed him.

However, at a press conference in the Kenyan port of Mombasa, where the Alabama docked on Saturday, the crew hailed Phillips as a hero.

"Everyone you see here today has the captain to thank for their lives and their freedom," Chief Mate Shane Murphy said.

Phillips is on board the USS Boxer, one of three US vessels that rushed to the scene of the hostage drama, recovering from the five- day ordeal and being debriefed.

The drama began to unfold on Wednesday, when four armed pirates boarded the Alabama using grappling hooks.

Crew members forced the pirates to retreat to the Alabama's lifeboat with Phillips, who the crew said gave himself up as a hostage to safeguard the lives of his 19 American crew.

The pirates were quickly hemmed in by warships, part of a coalition force based in the Gulf of Aden, as negotiations to free Phillips got underway.

Phillips failed in an attempt to swim to the Bainbridge on Thursday and was tied up to prevent further escape plans.

He was only freed when the on-scene commander judged that Phillips' life was in imminent danger and ordered snipers to open fire from the Bainbridge.

The order to open fire if Phillips was under threat came directly from Obama.

Murphy asked Obama to tackle Somali pirates, who have been wreaking havoc in the Gulf of Aden and surrounding region for years.

"We'd like to implore President Obama to use all of his resources to increase the commitment to end the Somali pirate scourge," Murphy said.

It was the second military action in three days against pirates in the region. French naval forces on Friday stormed a yacht, where pirates were holding a French family hostage. Two other pirates and one hostage were killed in the action, in which four hostages were freed.

There are fears that the two operations may lead to pirates becoming more violent.

Some pirate groups have already vowed to avenge their colleagues and to kill any American or French hostages taken in the future.

In a separate incident Monday, mortars were fired at the plane of US Congressman Donald Payne as he flew out of the Somali capital Mogadishu, but there was no evidence of a link with the pirate threats.

The airport in Mogadishu is often shelled as planes land and depart and any US official visiting Somali is a prime target for the Islamist insurgents fighting the government.

Payne's spokeswoman, Kerry McKenny, told CNN that a mortar was fired at the plane as they were leaving the city's airport, "but they did take off safely."

US State Department spokesman Robert Wood said Payne had departed Somalia and was "safe, unharmed," but could not confirm the details of the incident.

Wood refused to comment on the latest threats coming from Somali pirates, but he said the US was determined to work with international forces to regain control of the waters off Somalia.

"These folks are bandits. They're lawless," Wood said. "They're a bunch of criminals and we've got to prevent them from carrying out these types of attacks in the future."

Piracy has spiked in recent weeks after a brief lull due to bad weather.

In 2008, pirates seized more than 40 vessels in and around the Gulf of Aden and collected tens of millions of dollars in ransoms, prompting the international community to send warships to the region.

Around 15 warships from the European Union, a US-led coalition task force and individual countries such as Russia, India and China patrol an area of about 2.85 million square kilometres.

Pirates, who are venturing farther into the Indian Ocean to avoid the patrols, have attacked 18 ships over the last three weeks, according to the US Navy.

Five of those ships are in pirate hands, joining eight others that have been held for months. Over 200 seamen are being held by pirates.

The latest ship to be taken was an Italian tugboat, The Buccaneer, which was seized on Saturday. It has 16 crew members on board, including 10 Italians.

Reports said that the boat was spotted off the Somali coast near the pirate stronghold of Eyl on Monday.

International observers have long said the only way to nip piracy was to attack the pirates on land.

Defence officials said the plan, to be submitted to the Obama administration, would only be carried out with the backing of the Somali people.