TEL HAZEKA, Golan Heights – Israeli tanks struck a Syrian artillery launcher Monday after a stray mortar shell flew into Israel-held territory, the first direct clash between the neighbors since the Syrian uprising began nearly two years ago.

The confrontation fueled new fears that the Syrian civil war could drag Israel into the violence, a scenario with grave consequences for the region. The fighting has already spilled into Lebanon, Jordan and Turkey.

"We are closely monitoring what is happening and will respond appropriately. We will not allow our borders to be violated or our citizens to be fired upon," Prime Minister Benjamin Netanyahu said Monday in a speech to foreign ambassadors.