ISTANBUL (Reuters) - Turkish authorities detained the wife of Abu Omar al-Shishani, a senior Islamic State commander killed in combat two years ago, in a counter-terrorism operation in Istanbul this month, police said late on Thursday.

Dubbed Islamic State’s “war minister” and a close adviser to the extremist group’s leader, Abu Bakr al-Baghdadi, the Georgian Shishani was killed in action in the Iraq district of Shirqat, south of Mosul, in July 2016.

His wife was one five people detained in simultaneous raids across Istanbul on the night of July 4 that targeted people believed to have connections with conflict zones and actively seeking to carry out attacks, police said in a statement.

Her identity as Sishani’s wife was only discovered following several days of questioning, after her passport was determined to be fake, police said. They identified her only by the initials “S.D.”.

She was formally arrested by an Istanbul court on July 17 and jailed, police said. She had two sons with Shishani, police said, although the whereabouts of the children was unclear.

Born in 1986 in Georgia, then still part of the Soviet Union, Shishani once fought with Chechen rebels against the Russian military in the Caucasus province. He then joined independent Georgia’s military in 2006 and fought in its brief war with Russia two years later before receiving a medical discharge, according to U.S. officials.

He was arrested in 2010 for weapons possession and spent more than a year in jail, before leaving Georgia in 2012 for Istanbul and later Syria.

He decided to join Islamic State the following year and pledged his allegiance to Baghdadi. Prior to his death, he had ranked among America’s most wanted militants under a U.S. program that offered up to $5 million for information to help remove him from the battlefield.

Known as “the Chechen”, Shishani was one of only a few Islamist leaders with a professional military background and had several hundred fighters, mostly from ex-Soviet republics, under his command when he had come to prominence in a 2013 battle against Syrian President Bashar al-Assad’s forces in northern Syria.