The Israeli Defense Forces on Thursday sealed off an area adjacent to the Quneitra border crossing in the northern Golan Heights, shortly after the Syrian rebels seized it from forces loyal to President Bashar Assad. In an intense offensive launched in the early morning hours Thursday, opposition fighters managed to control Quneitra, the only crossing point on the demilitarized zone between Israel and Syria. \"The rebels have seized the crossing near the old city of Quneitra in the occupied Golan Heights,\" said Rami Abdelrahman, head of the UK-based Syrian Observatory for Human Rights. The Israeli Defense Forces (IDF) confirmed reports that rebels had seized the crossing, which is staffed by UN observers, on the Syrian-controlled side of the Golan Heights. \"The area was declared a closed military zone, though civilians residing there are allowed access to their homes,\" an IDF spokeswoman told Xinhua. She declined to say whether the army had taken additional measures to protect the Israeli side of the border. The IDF urged farmers to keep away from the border fence after a mortar shell landed in a nearby UN base. Israel has repeatedly voiced concerns that militants affiliated with global jihad, who are fighting alongside the rebels to topple Assad, will launch anti-Israel operations from the Golan, an area Israel captured from Syria in June 1967.