Islamist rebels detonated explosives planted in a tunnel under an armybase in northwestern Idlib on Wednesday, killing or injuring dozens, the SyrianObservatory for Human Rights said.The Britain-based group said the explosives blew up under a checkpoint inside WadiDeif army base, which opposition fighters have been trying to capture for more thana year.Video posted online showed a massive blast which hurled debris and soil dozens ofmetres (yards) into the air.Observatory director Rami Abdel Rahman said there was no precise toll in the attackyet, but that "dozens of soldiers have been killed or injured."The Islamic Front, a coalition of rebel groups, claimed the attack in a statement."The heroes of the Islamic Front, in coordination with the Furqan Brigade, blew up
the Wadi Deif base... after digging a 860-metre tunnel packed with 60 tonnes ofexplosives," it said.Wadi Deif is the one of the regime's last remaining strongholds in Idlib province,along with the nearby Hamadiyeh military base, which is also under rebel attack.Last week, at least 30 Syrian soldiers were killed in a similar attack involving
explosives planted in a tunnel under a checkpoint near Wadi Deif.A rebel told AFP at the time that the tunnel had taken 50 days to dig.Opposition fighters have also used the same tactic against facilities used by regimeforces in the northern province of Aleppo.