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   BEIRUT (AP) — Syrian rebels shot down a military helicopter in the country's east, killing eight government troops on board a day after opposition forces entered a sprawling military air base in the north, activists said Monday.

   In the past months, rebels fighting to topple President Bashar Assad have frequently targeted military aircraft and air bases in an attempt to deprive his regime of a key weapon used to target opposition strongholds and reverse rebel gains in the 2 year old conflict.

   The Britain-based Syrian Observatory for Human Rights on Monday posted a video online showing several armed men standing in front of the wreckage. One of the fighters in the footage says it's a helicopter that the rebels shot down late Sunday in the eastern province of Deir el-Zour, along Syria's border with Iraq.

   As the man speaks, the camera shifts to a pickup truck piled with bodies. The fighter is then heard saying that all of Assad's troops who were aboard the helicopter were killed in the downing. He says Islamic fighters of the Abu Bakr Sadiqq brigade brought down the helicopter as it was taking off from a nearby air base in the provincial capital of Deir el-Zour.

   The Observatory, which relies on a network of activists on the ground, said eight troops were killed.

   On Sunday, rebels occupied parts of a military air base in northern Syria after days of fighting with government troops who were defending the sprawling facility near the border with Turkey for months, the Observatory said.

   Assad's warplanes were pounding rebel positions inside the Mannagh air base Monday as clashes between rebels and government forces raged on, the Observatory said, adding there was an unknown number of casualties on both sides.

   The day before, rebels moved deep into the air base despite fire from government warplanes, capturing a tank unit inside the base and killing the base's commander, Brig. Gen. Ali Salim Mahmoud, according to another activists group, the Aleppo Media Center.

   The fighting came hours after Israeli warplanes struck areas in and around the Syrian capital, setting off a series of explosions as they targeted a shipment of highly accurate, Iranian-made guided missiles believed to be bound for Lebanon's Hezbollah militant group, officials and activists said.

   The attack, the second in three days and the third this year, signaled a sharp escalation of Israel's involvement in Syria's civil war. Syrian state media reported that Israeli missiles on Sunday struck a military and scientific research center near Damascus and caused casualties.

   The Syrian conflict started with largely peaceful protests against President Bashar Assad's regime in March 2011, but eventually turned into a civil war that has killed more than 70,000 people according to the United Nations.

   More than one million Syrians have fled their homes during the fighting and sought shelter in the neighboring countries such as Jordan, Lebanon and Turkey. Millions of others have been displaced inside Syria.