Cross-border shelling by the Syrian army wounded 25 people in northern Lebanon early Thursday, hours after twin air raids hit another border area, Lebanese security sources said.
The flare-up came as Syrian troops backed by fighters of its Lebanese ally Hezbollah pressed offensives on the Syrian side of the frontier, prompting an exodus of both rebels and civilians.
The artillery fire hit several homes in the Wadi Khaled area on Lebanon's northern border, a Lebanese security source said.
It was not immediately clear whether the 25 people wounded were Lebanese residents or Syrian refugees, the source added.
The shelling came a day after Syrian troops recaptured the town of Al-Hosn close to the border, sparking a new exodus of refugees adding to the thousands who had already sought shelter in mainly Sunni Muslim Wadi Khaled.
"The situation is very bad," Wadi Khaled doctor Tareq Dandashi told AFP.
"The whole of Al-Hosn has fled to Lebanon, and the Syrian army has been targeting them as they crossed over," he said
"In coordination with the Lebanese Red Cross, we have transported some 40 wounded."
The Al-Hosn area is home to the famed Krak des Chevaliers, one of the Middle East's best preserved Crusader castles.
The Syrian army bombarded rebel positions near the castle on Wednesday.
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The Al-Hosn offensive is one of two major operations by the Syrian army close to the border aimed at denying rebels supply routes for weapons.
Troops and Shiite militants of Hezbollah have also been engaged in a major offensive since November in the Qalamun mountains north of Damascus, where they recaptured the last major rebel stronghold Yabrud on Sunday.
The advances brought the Syrian government forces right up to Lebanon's eastern border, where air raids hit the mainly-Sunni Arsal area late on Wednesday, a security official said.
The strikes, which may have been targeting fleeing rebels, caused no casualties, the official told AFP on condition of anonymity.
"Syrian helicopters carried out two strikes against the areas of Wadi Ajram and Khirbet Yunin, on the outskirts of Arsal, just after 9:00 pm (1900 GMT)," he said.
The area, which hosts tens of thousands of Syrian refugees, has been hit by repeated cross-border fire in recent months, some of it deadly.
In January, a rocket attack on Arsal by the army killed eight people, including five children.
Smuggling routes used by opposition forces to move fighters and weapons back and forth between Lebanon and Syria pass through the Arsal area.
The area is widely sympathetic to the mainly Sunni rebels fighting the Alawite-led regime of President Bashar al-Assad.
On Wednesday, the Lebanese army arrested 15 Syrian men at an Arsal checkpoint, the National News Agency reported.
"The men had entered Lebanese territory with forged papers, and some of them were members of (Al-Qaeda's Syria affiliate) Al-Nusra Front," it said.