Belgian police in Brussels | John Thys/AFP via Getty Images Belgian terror sweep targets cousin of Brussels’ bombers Oussama Atar spent time in Iraq’s notorious Abu Ghraib jail.

Belgian authorities have identified the prime target of anti-terror raids on Thursday night as Oussama Atar, a cousin of two of the suicide bombers in the March attacks in Brussels.

Still at large, Atar is believed to have returned to Belgium from Syria about two weeks ago. He is a 32-year-old Belgian-Moroccan.

“Atar is the mentor and cousin of the El Bakraoui brothers. He radicalized them through the internet,” a senior Belgian law enforcement official told POLITICO.

Ibrahim El Bakraoui blew himself up at Zaventem airport, while his younger brother Khalid detonated his device at Maalbeek metro station. In all, 35 people died in the attacks.

Atar first travelled to the Iraq-Syria area in 2002 posing as a charity worker, but was arrested in 2005 and sentenced to 10 years in prison. He served sentences in several jails including the infamous Abu Ghraib prison and Camp Bucca, where he reportedly met Abu Bakr al-Baghdadi, the current leader of Islamic State.

He returned to Belgium in 2012 after his family ran a campaign for his release. He was arrested in 2013 while trying to escape to Tunisia. But he was released and disappeared.

According to Le Parisien, a French newspaper, on June 21 French intelligence received a “message de vigilance” about Atar saying he intended to come to France through Albania.

According to another senior counter terrorism official, Atar has a dangerous network, which has included Malika El Aroud and Imam Bassam Ayachi.

El Aroud is the widow of one of two men who carried out a suicide bombing in Afghanistan that killed the anti-Taliban commander Ahmed Shah Massoud.

“Atar was a contact of the radical imam from Molenbeek, Bassam Ayachi, who was arrested in Bari, Italy in 2008 and then released,” the counterterrorism official said.

He added that the imam had celebrated the wedding of El Aroud with Massoud’s assassin.