Syrian government forces are battling armed rebels on the other side of the Israeli-Syrian armistice line, which has been in place for decades.

The direct strike by Israel on Syria’s artillery unit was another example of how the conflict in Syria has escalated by spilling into neighboring countries. Hundreds of thousands of refugees have poured out of the country, with more than 408,000 in Turkey, Jordan, Lebanon and Iraq now registered with the United Nations. Shells fired from Syria have killed civilians in Lebanon, and in one episode last month, Islamic extremists attacked Jordanian soldiers on the border with Syria, killing a corporal.

On Monday, a Syrian MIG-25 jet bombed the rebel-held town of Ras al-Ain a few yards from the Turkish border, killing civilians, Syrian witnesses said. Five Turkish civilians were killed in October when a Syrian shell landed in Akcakale, another border town about 75 miles west of Ceylanpinar, an act that prompted the Turkish Parliament to revise engagement rules and allow the military to retaliate in case of a direct threat from the border region.

Israeli military officials have made it clear that Israel has no desire to get involved in the fighting in Syria. Israel had already filed complaints with the United Nations observer force that monitors the armistice agreement reached between the Israeli and Syrian forces after the 1973 war, and the United Nations has warned that the spreading violence could jeopardize the cease-fire between the two countries.