BEIRUT March 24 (Reuters) - Syrian troops backed by war planes battled on Monday to dislodge Islamist rebels from a border crossing and northern town in the coastal province of Latakia, heartland of President Bashar al-Assad's Alawite minority.
Fighters from the Islamic Front and al Qaeda-linked Nusra Front seized the Armenian Christian town of Kasab on Sunday after taking the nearby border crossing in an offensive which follows a string of recent rebel defeats further south.
Video footage released by activists showed fighters driving through the largely deserted Kasab, passing a municipal building and a shattered statue of Bashar's father Hafez, who ruled Syria for 30 years until 2000.
While the rebel advance has gained only a small pocket of territory, it has put Assad on the defensive and deprived him - at least for now - of the last border crossing from Turkey into government-held territory.
It follows months of advances by Assad's troops and Lebanese Hezbollah fighters near the capital Damascus and the Lebanese border, choking rebel supply lines and reasserting control of central Syria as the civil war enters a fourth year.
More than 140,000 people have been killed in the conflict and nearly half the population has been displaced but the coastal provinces of Latakia and Tartous have so far remained largely loyal to Assad and relatively unscathed.
Activists said authorities have sent reinforcements to the Kasab area to stem the rebel advances. State media said the army and National Defence Force militia were surrounding the rebels close to the border.
The Syrian Observatory for Human Rights monitoring group said there was heavy fighting on the eastern edge of Kasab and other areas near the border.
War planes were bombarding rebel positions and causing forest fires, it said, while television images showed smoke rising from the wooded border region.
Rebel fighters have also struck deeper into Latakia province, attacking the town of Solas to the south and firing rockets overnight into Latakia city, killing eight people.
Latakia port is the main transport hub for the international operation to ship Syria's chemical weapons out of the country for destruction, but the Observatory said the rockets did not land close to the port area.
Assad suffered a double blow on Sunday, with Turkey downing a Syrian jet it said strayed across the border and rebels killing a cousin of the president who led the local paramilitary force fighting alongside the army.
The shooting down of the Syrian plane further escalated tensions between the two countries.
"Nobody should attempt or dare to test Turkey's power," Turkish Foreign Minister Ahmet Davutoglu said on Monday. "Engagement rules are clear, and the response will be clear when our airspace is violated, and that response has been given."
Syria also accused Turkey of providing military cover for the rebel attack on Kasab, saying Turkish forces fired into Syrian territory. (Reporting By Dominic Evans in Beirut and Ece Toksabay in Istanbul; Editing by Angus MacSwan)