BEIRUT, Jan 31 (Reuters) - Unidentified militants involved in Syria's civil war clashed with the Lebanese army on Friday near the porous border between the countries, security sources said.
It was a further sign of spillover from Syria's conflict which has destabilised its small Mediterranean neighbour and whipped up sectarian tensions.
About four km (2.5 miles) inside the Syrian border, rebels killed at least five Syrian soldiers and border guards in an attack on two villages near Talkalakh, the Britain-based Syrian Observatory for Human Rights monitoring group said.
Soon after, around 15 artillery shells fired from Syria landed inside northern Lebanon as Syrian government forces pursued rebels near the frontier. A man was killed and at least two others were wounded in the clashes.
Hours later, the Lebanese army surrounded a mountainous area near the border and exchanged fire with gunmen holed up there, the sources told Reuters.
The nationality of the gunmen was not clear. Syrian rebels and Lebanese Sunni Muslim militants who support the Sunni-led revolt against Syrian President Bashar al-Assad travel relatively unhindered between Syria and Lebanon.
Lebanon's frontier with Syria is not straight or always well marked, making it difficult to determine where one country's territory ends and the other's begins.
Many Sunnis in north Lebanon say the Lebanese army is taking orders from the Syrian government, which has a history of involvement in Lebanese politics and security institutions. More than 130,000 people have been killed in Syria's conflict, which began with popular protests against Assad in March 2011 but evolved into a civil war after a bloody crackdown by security forces.
The violence has spread into Lebanon, where car bombings, rocket attacks, and sectarian gunbattles have become more common, especially since Lebanese Shi'ite Hezbollah militants began openly fighting in Syria on Assad's side last year. (Reporting by Stephen Kalin; Editing by Mark Heinrich)