8 killed in Syria helicopter assault, as new reports surface of chemical weapon use Eight government security troops were killed Monday when their helicopter was shot down, according to Syrian opposition forces, as reports emerged that the rebels may have used chemical weapons in their two-year fight to remove President Bashar Assad from power. The rebels denied the charge, according to a report in The New York Times. The activist group Syrian Observatory for Human Rights posted video Monday showing combatants standing in front of what looked like the remains of a downed helicopter. The group says the chopper was carrying eight government troops when it was shot down in eastern Syria. In recent months, rebels fighting to topple Assad have frequently targeted military aircraft and air bases in an attempt to deprive the Assad regime of a key weapon used to target opposition strongholds and reverse rebel gains. Meanwhile, human rights investigators from the United Nations said they have "strong suspicions" that Syrian rebels might have used chemical weapons in their fight against government forces, according to the Times. A lead UN investigator, Carla del Ponte, said the UN independent commission of inquiry on Syria has not yet seen evidence of President Assad's forces having used chemical weapons. Our investigators have been in neighboring countries interviewing victims, doctors and field hospitals and, according to their report of last week, which I have seen, there are strong, concrete suspicions but not yet incontrovertible proof of the use of sarin gas, from the way the victims were treated. This was use on the part of the opposition, the rebels, not by the government authorities, " del Ponte told Swiss-Italian television over the weekend. Del Ponte -- one of four investigators mandated by the UN Human Rights Council to report on Syria -- did not provide any details on where or when the nerve agent sarin may have been used. The report followed claims last month that government troops had used sarin gas in the war, but that has not been proved. The use of chemical weapons is banned under international law. Members of the opposition say there's no truth to the reported findings. Maj. Gen. Adnan Sillo -- a defector from the Syrian military who specialized in chemical warfare -- said the claims of sarin use came when Syria had already crossed the "red line" laid down by President Obama as a warning to Assad not to use chemical weapons. "This claim is a big lie," he said, according to The New York Times. "The Syrian regime has used the chemical weapons against civilians many times," most recently near Idlib in the north of the country, he said. And there is no doubt that the regime will use it more often as this is its strategy in the war since the beginning of oppressing the uprising, to move gradually. The accusations come after Assad's government publicly rebuked Israel for airstrikes on military targets near Damascus early Sunday, saying the attack "opened the door to all possibilities." The strike on a military complex near the Syrian capital of Damascus killed at least 42 Syrian soldiers, a group of anti-regime activists said Monday, citing information from military hospitals. The Syrian government has not released a death toll, but Syrian state media has reported casualties in Sunday's predawn airstrike, Israel's third into Syria so far this year. The Britain-based Syrian Observatory for Human Rights said about 150 soldiers are normally stationed in the area that was targeted, but that it was not clear how many were there at the time of the strike. Israel's government has not formally confirmed involvement in strikes on Syria. However, Israeli officials said the strikes were meant to prevent advanced Iranian weapons from reaching Lebanon's Hezbollah militia, an ally of Syria and foe of Israel. The officials spoke on condition of anonymity because they were not authorized to discuss covert military operations. Iranian Foreign Minister Ali Akbar Salehi warned Monday that Israel was "playing with fire," but gave no other suggestions of possible consequences, according to the official Islamic Republic News Agency. Syria's government called the attacks a "flagrant violation of international law" that has made the Middle East "more dangerous." It also claimed the Israeli strikes proved Israel's links to rebel groups trying to overthrow Assad's regime. Israel on Monday signaled a return to "business as usual," with Prime Minister Benjamin Netanyahu arriving in China for a scheduled visit. The Israeli military deployed two batteries of its Iron Dome rocket defense system to the north of the country Sunday. It described the move as part of "ongoing situational assessments." Hezbollah fired some 4,000 rockets into Israel during the 2006 war, and Israel believes the group now has tens of thousands of rockets and missiles. The Iron Dome deployment followed a surprise Israeli drill last week in which several thousand reservists simulated conflict in the north. In another possible sign of concern, Israel closed the airspace over northern Israel to civilian flights on Sunday and tightened security at embassies overseas, Israeli media reported. Israeli officials would not confirm either measure. Israel's deputy defense minister, Danny Danon, would neither confirm nor deny the airstrikes. He said, however, that Israel "is guarding its interests and will continue to do so in the future." Syria and its patron Iran have hinted at possible retribution over the strikes, though the rhetoric in official statements has been relatively muted. Click for more from the New York Times.