After Syrian rebels allegedly robbed 30 trucks carrying goods from Turkey into Syria, Turkish officials announced the closure Saturday of a Syrian-Turkish border crossing.

The crossing at Cilvegozu would be shuttered in response to the attack, said Celalettin Lekesiz, governor of the Turkish state of Hatay. He said it was unclear when the crossing would reopen.

Nine trucks were set on fire in the attack. Food and medicine were stolen from other trucks, the drivers of which had been waiting days at the crossing.

Syria's rebels have been making advances in recent days, taking control of multiple border crossings between Syria and Iraq, Turkey and Jordan.

Meanwhile, UN Secretary General Ban Ki-moon said he is sending an envoy to Syria to assess the situation there, as government forces and rebels fight for control of key cities in the country.

Ban said he will send Undersecretary General for Peacekeeping Operations Herve Ladsous to Syria to assess the situation. Ladsous would be accompanied by the top UN military adviser, General Babacar Gaye, to lead the United Nations Supervision Mission in Syria in this critical phase.

"We continue to push for a peaceful solution. And I am in contact with regional and international leaders, and I am working closely with the joint special envoy, Kofi Annan," Ban told a press conference in Croatia.

His statement comes one day after the United Nations Security Council voted unanimously to extend an observers' mission by 30 days. The team's mandate was extended with the understanding that the observers would assist a transition in Damascus or pull out if no political solution is found to end the 17-month conflict.

Ban's statements also come after Russia and China vetoed a resolution to impose further sanctions on the government of Syrian President Bashar Assad.