The men, employees of Devon-based Anti-Piracy Maritime Security Solutions (APMSS), were plucked out of the Gulf of Aden early yesterday morning by a German navy helicopter. The Liberian-flagged Biscaglia, with 25 Indian and two Bangladeshi crew members remaining on board, was taken by the pirates to the Somali coast.
Nick Davis, chief executive of APMSS, said the guards, all former military servicemen, had leapt into the sea after coming under heavy attack from pirates using automatic weapons and rocket-propelled grenades.
"Reports remain confused, however we believe that the embarked three-man APMSS security team ... were able to mount sustained, non-lethal resistance, denying the attackers access to the ship long enough for the ship's operating crew to seek safety below decks and to summon assistance from coalition warships," he said in a statement.
The captain of the Nivôse, a French warship that was patrolling nearby, said that the Biscaglia sent out a distress signal at 7.48am after being threatened by five pirates in a fishing boat. The gunmen boarded the vessel using a ladder.
Davis said that he had spoken to his team leader on the phone and been assured that the pirates' violence had "forced them to reluctantly leave the vessel". The pirates fired upon the guards in the water and then attempted to use the ship to run them down, he said.
All three men, who were rescued when a German Lynx helicopter responded to the distress call and were later transferred to the Nivôse, were said to be "well, with no reported injuries".
The incident highlights the difficulties for shipping companies using the Gulf of Aden, which is the shortest route between Asia and Europe.
While the firms have been encouraged to use private security personnel on board, many are reluctant to employ armed guards for safety and legal reasons. A deadly error by the Indian navy last week, which claimed to have sunk a pirate ship only to find that it was a newly hijacked Thai ship whose crew was still on board, has further illustrated the need for caution.
APMSS was formed in July when it became clear that piracy was a major threat to one of the world's busiest shipping routes. It claims to offer a "non-lethal solution" to protect vessels in the waters off Somalia.
"We only employ ex-servicemen capable of operating in the civil maritime sector who can make the full ships complement at every level feel safe without putting the fear of God into them at heightened security time," the firm says on its website.
The main weapon used by its guards is a magnetic audio device, which is billed as the sonic equivalent of a laser, and blasts "directional, high quality verbal challenges" over long distances, according to one British vendor. APMSS said the device prevented a pirate attack on chemical tanker it was guarding earlier this month.
The fate of the other Britons caught up in Somalia's piracy web remains unclear. The 330-metre Saudi supertanker Sirius Star is anchored off Harardheere, on Somalia's north-eastern coast. The vessel, which was seized on November 15, has two Britons among its crew, Peter French and James Grady.
Authorities have until Sunday to pay the ransom of $25m (£16m). Lord Peter Levene, Lloyd's chairman, told Channel 4 news on Wednesday he thought it was "highly likely" that the owners of the vessel, which was carrying 25 crew members and 2m barrels of oil, would pay the money. Negotiations are continuing, and the captured Britons say the crew is being treated well.
A British newspaper correspondent who had been reporting on the piracy surge from Bossaso in the northern Puntland state was kidnapped earlier this week, along with a Spanish photographer.
Local police said yesterday that the journalists had been taken to a mountainous region, and that they were trying to negotiate with local clan elders for their release.