THESSALONIKI, Greece (AP) — Greek police say they have arrested two men suspected of possessing weapons and attempting to travel to Syria to join the Islamic State group.

One of those arrested was a 29-year-old Serbia-born Swedish citizen who was released from prison in 2011 after serving six years for possessing explosives and threatening to carry out a terrorist attack, a police officer told The Associated Press Sunday. The man had been arrested and convicted in Bosnia before he was transferred to serve the last part of his sentence in Sweden.

He was arrested again Thursday near the Greek-Turkish border alongside a 20-year-old originally from Yemen. Both were traveling on Swedish passports and Greek police said they found two long knives, a rifle holster and military uniforms in their luggage.

The police officer, who demanded anonymity because he wasn't authorized to speak about an ongoing investigation, said they are believed to have been on their way from Sweden to Syria. They had left Sweden by car and then flown from Copenhagen to Athens. After that, they traveled by bus to Thessaloniki and then to the northeastern city of Alexandroupolis, where they were arrested while trying to find local transport to the Turkish border, which they planned to cross on foot.

An official police statement said the two were arrested during a routine inspection, but the officer told the AP they had been tracked throughout their journey.

Sweden's Foreign Ministry confirmed that two Swedish citizens had been detained in Greece but gave no other details.

Sweden's security police are co-operating with Greek police and security officials on the case, security police spokeswoman Sirpa Franzen said, but couldn't give any other details.

The two suspects will appear before a magistrate on Tuesday.

Demetris Nellas in Athens, Greece, and Jari Tanner in Helsinki contributed to this report.

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