Croatia sold a record amount of its old munitions caches to Saudi Arabia in 2016, despite growing evidence these weapons may be arriving in Syria.

In the first nine months of 2016, Zagreb sold Riyadh $81.7 million worth of aging ammunition left over from its civil war in the 1990s - nearly double that sold in the four years previous.

"It is quite likely that the exports come from old ammunition," said Igor Tabak, a Croatian defence analyst, adding that Croatia does not currently manufacture ammunition.

Croatian records show that it sold 5,000 tons of ammunition in 2013 and 2014 - which is the same amount as was sold in the entire decade previous.

A 2013 investigation by The New York Times showed that Croatia was one of the first countries to start providing weapons to the Syrian rebels in 2012.

An analysis of end user certificates and flight records showed weapons were flown via military cargo flights from Zagreb to Jordan, where they were then allegedly sent to Syrian rebels via trucks.

There have been numerous videos and pictures published by Syrian rebels showing them using Croatian made ammunition.

A YouTube video, published by 'Sword of al-Sham' on May 18, 2016 purportedly showed Croatian RAK-12 rockets marked "AL."

These weapons are sometimes falling into the wrong hands however.

"We've now seen groups like Islamic State and Jabhat al-Nusra using these weapons, although how they acquired them is unclear," said Eliot Higgins, a London-based citizen journalist.

Government receipts show that the arms trade between Croatia, Jordan and Saudi Arabia did not begin until 2012, but since then, almost all of Croatia's ammunition has been sold to either Jordan or Saudi Arabia.