DUBAI (Reuters) - Yemen’s Houthi forces denied detaining a U.S. citizen and said he had been kidnapped by unknown gunmen in the capital Sanaa, a statement from the movement said.

Colleagues of Danny Lavon Burch, an engineer who had been working in Yemen since the late 1980s, said on Monday that Houthi forces had detained him in Sanaa.

The Iran-aligned Houthis and their ally former president Ali Abdullah Saleh control much of northern Yemen, including Sanaa, and are battling a Saudi-led coalition that is trying to restore the internationally recognized government.

An armed gang was behind “the criminal and cowardly act” of kidnapping Burch, a statement carried by the Houthi-controlled state news agency SABA said late on Wednesday.

“The security services are tracking the perpetrators of the kidnapping and they will be brought to justice,” it said.

His wife, Nadia Burch, told Reuters earlier this week that her husband had been seized on Saturday after taking their children to school. He has worked in Yemen since the late 1980s, currently with the oil company Safer, said Burch, a Yemeni.

“He has no problems or disputes with anyone, which is why he didn’t leave as others did,” she said. “I ask for the release of my husband and his safe return to me.”

She said the kidnappers had not contacted her and she was unsure of their identity.

A U.S. State Department official said they were aware and concerned about the report of Burch’s disappearance.

More than 10,000 people have been killed in Yemen’s civil war. It began in March 2015 when the Houthis advanced on the interim headquarters of President Abd-Rabbu Mansour Hadi in the southern port city of Aden, forcing him to flee the country and seek Saudi help.