ANKARA (Reuters) - Turkish soldiers shot into the air and fired tear gas to prevent hundreds of people, many of them believed to be smugglers, from trying to cross into Turkey from Syria, the Turkish military said on Tuesday.

A group of 1,500-2,000 people tried to approach the border and threw stones at military patrol vehicles sealing the Turkish border at the town of Ogulpinar in Hatay province in the early hours of Tuesday.

Soldiers dispersed the group by firing tear gas after issuing warnings in Arabic and Turkish, the military said.

It was the second such incident in as many days. The military said around 1,000 people had tried to enter Turkey illegally on Monday and that it had seized some 6,000 liters of diesel from them.

In a separate confrontation in the same region, Turkish soldiers fired pre-emptive shots at a group of 300-350 people on horseback who were also trying to cross the border on Tuesday.

Smuggling of fuel and other goods has risen on Turkey's 900 km (560 mile) frontier with Syria, triggering a growing number of confrontations over the past month and underscoring Ankara's concerns that Syria's more than two-year-old civil war is fuelling lawlessness and dragging in neighboring states.

With its hilly terrain and thick vegetation, Hatay, a panhandle province that juts down into Syria, makes a relatively easy crossing point for smugglers and Syrian rebel fighters, as well as refugees fleeing the fighting.

Turkish troops have been wounded and have returned fire in a spate of border incidents over the past month. A Turkish border patrol last week killed a civilian trying to cross illegally into Syria after the group of men he was with opened fire.

Turkey shelters around 500,000 Syrian refugees as well as rebels fighting to overthrow Syrian President Bashar al-Assad, but while backing the Syrian insurgents, it denies arming them.

In the most serious spillover of violence in weeks, two Turkish teenagers were killed last week by stray bullets fired during clashes between Islamist militants and Kurdish fighters in a Syrian border town several hundred kilometers east of Hatay.

(Reporting by Humeyra Pamuk; Editing by Nick Tattersall and Gareth Jones)