SARAJEVO (Reuters) - Bosnian police have arrested an Islamist militant for terrorism offences in Bosnia, prosecutors said on Friday, and a Balkan news service said the man was believed to assisted a 2011 attack on the U.S. Embassy in Sarajevo.

A state prosecutor’s statement said the man was taken into custody at Sarajevo airport and was also suspected to have fought for Islamic State and rival Syrian militant group Nusra Front, an ex-al Qaeda affiliate, in Iraq and Syria.

It added that the detainee had been under investigation on suspicion of forming a terrorist group in Bosnia.

Citing sources close to the investigation, the Balkan Investigative Reporting Network (BIRN) said the arrested man was believed to have assisted in the attack on the U.S. Embassy in which a Bosnian gunman shot and wounded a police guard before being wounded by a sniper and then apprehended.

The gunman, also an Islamist militant, was jailed for 18 years after his conviction but his term was reduced to 15 years in 2013 after he apologized for the attack.

Bosnian Muslims generally practice a moderate form of Islam but some have adopted radical Salafi Islam from foreign fighters who came to the country during its 1992-95 war to fight alongside Muslims against Orthodox Serbs and Catholic Croats.

Some radicalised Bosnians joined Islamic State to fight in Syria and Iraq. But police say there have been no more Bosnians leaving for Syria or Iraq since 2015, and that more than half of those who have returned home have been jailed under a law prohibiting fighting in wars in foreign countries.