The sources, who spoke on condition of anonymity, said the Colombians' experience fighting leftist guerrillas and drug traffickers in their home country made them attractive recruits for the UAE, whose relatively inexperienced army is part of an Arab coalition helping Yemen's government fight a war against Huthi rebels.
"Colombian soldiers are highly prized for their training in fighting guerrillas," one source, a Colombian former army officer, told AFP in Bogota.
The presence of Colombian troops in Yemen's bloody conflict further complicates what is already a messy proxy war pitting Iran, which backs the rebels, against a US-backed Arab coalition led by rival regional heavyweight Saudi Arabia.
Since the rebels began seizing large swaths of territory in July 2014, the conflict has left 6,000 dead and 28,000 wounded, many of them civilians, according to the United Nations.
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Colombian soldiers are frequently recruited by international private security firms for jobs in places like Iraq, Afghanistan and Sudan.
The source, a 48-year-old man who left the army in the late 1990s, was himself formerly employed by Blackwater, the controversial US company now known as Academi that was contracted by the Pentagon to provide military and security services in Iraq.
Latin Americans were popular with firms like Blackwater, he said: in all, 1,500 Colombians, 1,000 Peruvians, 500 Chileans and 250 Salvadorans were contracted in Iraq between 2004 and 2006.
He said that from around 2010 the UAE began recruiting Colombians for a private army it was forming at a base in the middle of the desert called Zayed Military City.
Prized as special forces commanders or Blackhawk helicopter pilots, the Colombians are paid around USD 3,300 a month - five times less than equivalent American contractors, but a small fortune by Colombian standards, he said.