Thousands of assault rifles such as AK-47s, mortar shells, rocket launchers, anti-tank weapons and heavy machine guns are being routed through a new arms pipeline from the Balkans to the Arabian peninsula and countries bordering Syria.
The suspicion is that much of the weaponry is being sent into Syria, fuelling the five-year civil war, according to a team of reporters from the Balkan Investigative Reporting Network (BIRN) and the Organised Crime and Corruption Reporting Project (OCCRP).
Arms export data, UN reports, plane tracking, and weapons contracts examined during a year-long investigation reveal how the munitions were sent east from Bosnia, Bulgaria, Croatia, Czech Republic, Montenegro, Slovakia, Serbia and Romania.
Since the escalation of the Syrian conflict in 2012, the eight countries have approved €1.2bn (£1bn) of weapons and ammunition exports to Saudi Arabia, Jordan, the United Arab Emirates and Turkey – key arms markets for Syria and Yemen.
In the past, the region had virtually no track record of buying from central and eastern Europe. But purchases appear to be escalating, with some of the biggest deals approved in 2015.
Revealed: the £1bn of weapons flowing from Europe to Middle East