* Police, spies fret over Canadians fighting abroad
* New law would prevent suspects from leaving Canada (Adds security expert on Canadian involvement)
By David Ljunggren
OTTAWA, Jan 21 (Reuters) - The likely involvement by Canadians in a deadly hostage taking at an Algerian gas plant adds to Ottawa's concerns about militant citizens who have trained with radical groups abroad or who seek to use violence to further their cause.
Algerian Prime Minister Abdelmalek Sellal said on Monday that a Canadian gunman had coordinated a four-day siege, which ended with Algerian forces storming the BP plant on Saturday. At least 80 people were killed, including 37 foreigners.
Canada condemned the attack and said it was seeking more details from the Algerian authorities. At a news conference on Monday, Sellal gave the alleged Canadian militant's name only as Chedad.
With some bodies burned beyond recognition and Algerian forces still combing the site, many details of the siege and hostage takers were still unclear.
"We've heard (there were) at least two Canadian nationals, possibly at least one person who spoke English with a North American accent," said U.S. counter-terrorism expert Evan Kohlmann.
Canada, one of the few western nations actively seeking immigrants, has a large number of ethnic communities.
While the number of Canadians known to have been involved in radical actions appears small, they include Ahmed Said Khadr - a close associate of Osama Bin Laden - who died in a clash with Pakistani forces, and his son Omar, who pleaded guilty to killing a U.S. soldier in Afghanistan and conspiring with al Qaeda.
Omar Khadr, aged 15 at the time of the shooting, was transferred to a Canadian jail last September after spending almost 10 years in the U.S.-run Guantanamo prison.
Canadian resident Ahmed Ressam, an Algerian citizen, tried to cross the U.S. border on a mission to blow up Los Angeles airport in 2000 and is serving 37 years in a U.S. jail.
"We are seeing a consistent volume of individuals being radicalized who are looking to travel abroad to either participate in, train for, or conduct terrorist acts," senior Canadian police office James Malizia said late last year in testimony to a House of Commons committee.
"The number of people traveling abroad is still very real and a very serious concern for us, as is the number of people who could potentially fall off the radar once they've left," said Malizia, an assistant commissioner with the national security branch of the Royal Canadian Mounted Police.
Canada's government introduced draft legislation last February making it illegal for Canadians to travel abroad to commit acts of terrorism. Malizia gave no details on how many Canadians might have left the country for such purposes.
But in April 2012, the head of Canada's spy agency said as many as 60 Canadians had traveled - or tried to travel - to Somalia, Afghanistan, Pakistan and Yemen to join al Qaeda-affiliated groups and engage in terror-related activities.
Dick Fadden, director of the Canadian Security Intelligence Service, has often said he is worried by radicalized young Canadians. In 2006, Canadian police broke up a gang of young Muslim men, the so-called Toronto 18, who had plotted to bomb high-profile targets in Toronto and Ottawa.
Fadden described the group was an example of "second- or third-generation Canadians, who in some ways are relatively well integrated" but who had become "appallingly disenchanted with the way we want to structure our society".
Immigration Minister Jason Kenney, citing the Toronto 18, told Reuters on Monday that "we're tightening immigration security. But many radicalized Canadians are born here".
Jez Littlewood, director of the Canadian Centre of Intelligence and Security Studies at Ottawa's Carleton University, said Canada was not a particular hotbed for sending militants abroad, despite its multicultural nature.
"The radicalization of the communities in Canada in relative terms has been lower that one might have expected," he told Reuters, citing the number of British and American nationals arrested on suspicion of planning or taking part in attacks.
Under the draft bill, which is currently being studied by Parliament, people trying to leave Canada to take part on attacks abroad could jailed for up to 14 years.
Canada has no exit controls and cannot tell when someone leaves the country, a particular challenge to the authorities. (Additional reporting by Randall Palmer and Mark Hosenball; Editing by Janet Guttsman and Peter Galloway)