* Canadians were two young men from London, Ontario -police
* Police appeal for public help for more details
By David Ljunggren
OTTAWA, April 4 (Reuters) - Police on Thursday confirmed the identity of two young Canadians who took part in a violent attack on an Algerian gas plant in January and asked the public to help them find out how the two left the country.
Around 70 people, including the two Canadians, were killed when Algerian troops stormed the Tigantourine desert gas plant and ended the siege. The Royal Canadian Mounted Police identified the two men as Xristos Katsiroubas and Ali Medlej.
Canadian media say Katsiroubas, 22, and Medlej, 24, were high school friends from London, in the central Canadian province of Ontario.
Marc Richer, a spokesman for the RCMP, said the force wanted to hear from anyone who knew how the two men had left Canada and who might have helped them.
"People tend to look to the police and the police having all the answers. The reality is we need the public's help. This is a community issue. Everybody has a role to play in this," he told a news conference.
The RCMP was also seeking information about anyone else who might be contemplating terrorist plots abroad, he added.
Richer said police had been investigating the two men for a number of months but did not give details.
He declined to confirm media reports that Aaron Yoon, a former schoolmate of the two men, had left Canada with them and was under arrest in the West African nation of Mauritania.
A Canadian Foreign Ministry official, asked about the reports, said he was aware that a Canadian had been detained abroad but gave no details.
The Canadian Security Intelligence Service spy agency has repeatedly warned of the dangers of radicalized Canadians traveling abroad to engage in violence.
"Radicalization to violence is not a new phenomenon. It is not exclusive to any single ethnic or interest group," said Richer.
"Ultimately, countering radicalization to violence also depends on the public taking an active role in intervention, including assisting law enforcement by reporting suspicious and illegal activities."
Earlier this week, the Canadian Broadcasting Corporation cited police sources as saying Katsiroubas, who converted to Islam from the Greek Orthodox faith, was likely to be the attacker who survivors described as being blond-haired and speaking fluent "North American English."
The Canadian Security Intelligence Service says it knows of dozens of Canadians in their early twenties who have traveled or tried to travel overseas to take part in terrorism-related activities.
A Canadian-Lebanese dual national was involved in the 2012 bombing of a tourist bus in Bulgaria that killed five Israeli tourists. (Editing by Mohammad Zargham)