beirut lebanese security force arrest former mayor town arsal near syrian border saturday connection capture lebanese soldier security source say ali al-hujeiri also stand accuse collusion nusra front islamist group al qaeda former syria branch source say militants nusra front islamic state briefly overrun arsal 2014 capture number soldier withdraw clash army nusra front release 16 soldier 2015 exchange release jail islamists islamic state kill nine soldier capture group drive last foothold syria-lebanon border recent separate offensives army lebanese shi ite group hezbollah immediately clear group capture soldier hujeiri accuse lebanese president michel aoun say week army investigate circumstances lead capture soldier kill islamic state lebanon arrest former mayor border town near syria security source