Updated

A Syrian man suspected of planning a radical Islamic terror attack in Germany committed suicide in prison, officials said Wednesday.

The German news agency dpa reported that Jaber Albakr, 22, was found hanged in his cell in the city of Leipzig. Der Spiegel reported that Albakr had been under constant surveillance and was on a hunger strike.

Justice Ministry spokesman Joerg Herold told The Associated Press that Albakr killed himself sometime in the evening, but that the incident was still being investigated.

Albakr, who arrived in Germany last year, was arrested Monday after three fellow Syrians tied him up and alerted police. Two days earlier, police raided an apartment in the eastern city of Chemnitz, where they found "several hundred grams" of a volatile explosive and a homemade bomb vest.

Albakr, who had been under surveillance by German domestic intelligence since last month, was observed exiting the apartment building and authorities fired a warning shot. He nevertheless was able to elude police on the scene and flee the city, prompting criticism of Saxony state authorities.

Interior Minister Thomas de Maiziere said earlier Wednesday that "there was a check against security authorities' data in 2015, but without any hits." He added "it's not clear when he was radicalized."

Authorities believe the suspect had links to ISIS. Security officials believe Albakr intended to attack a passenger train before setting his sights on one of Berlin's airports.

German media have reported that after his initial arrival, Albakr later returned to Syria through Turkey and then came back to Germany. German federal authorities have not commented on the reports.

The Associated Press contributed to this report.