Six people have died in an explosion in a Turkish border town that has become a vital staging post for arms convoys to Syrian rebels.

Initial reports suggested that a consignment of live ammunition had exploded as it was being smuggled into Turkey from Syria, according to the provincial governor of Turkey's Hatay province.

Five Syrians died in the blast and a Turkish citizen later died of his wounds, the governor's office said. Three others were injured in the explosion, according to the Doğan news agency.

According to official claims, ammunition mixed with scrap metal was being taken from Syria into Hatay but reports about the incident conflicted.

The blast occurred at an ammunition depot in the Altinozu district, said officials, although other reports said that it happened in a vehicle that was transporting scrap metal on the Syrian side of the border.

Turkish soldiers and smugglers clash daily in the area.

The wild, hilly province of Hatay juts into Syria, making it a preferred crossing-point for smugglers, rebels and refugees fleeing the war.

Turkey has been a leading voice in calling for President Bashar al-Assad's overthrow. While it has consistently denied arming the rebels, it admits giving them shelter. An estimated 500,000 refugees have fled to Turkey.

An illicit cross-border trade in goods including fuel and basic commodities has flourished since hostilities broke out in 2011, providing a lifeline for impoverished Syrians.

NTV and CNN-Turk said that a group of smugglers was completing a deal for the sale of scrap metal collected in Syria and destined for Turkey, which pinpointed the blast scene as Azmarin, northern Syria, near a border crossing into Hatay province.

Local reports have suggested that intelligence agents from the US, Turkey and Qatar used a converted Turkish military garrison in Antakya, Hatay, as a Free Syrian Army command centre.<ins>

Syrian rebel forces are thought to have received more than 400 tonnes of weapons, including anti-aircraft guns and shoulder-fired missiles.

Witnesses in August reported seeing weapons being loaded on to more than 20 trucks which crossed into northern Syria.