Security sources told The Daily Star newspaper in Lebanon that a "heavy deployment" of Lebanese forces, accompanied by U.N. peacekeepers, was sent to the southern border to respond to Israeli military activity.
The newspaper reports 10 Israeli troops, a tank and two bulldozers moved close to the Blue Line. There, they dug trenches to hide military tanks.
The Blue Line is a U.N.-demarcated border between Israel and Lebanon. The U.N. Interim Force in Lebanon had said the border is relatively calm despite tensions in the region because of the Syrian civil war and recent fighting between Israel and Hamas.
Hezbollah Secretary-General Hassan Nasrallah this week warned Israel that his military brigades would fire missiles at Tel Aviv should Israeli forces attack Lebanon.
Hezbollah and Israel went to war in 2006. A U.N. mandate that brokered a cease-fire calls on Hezbollah to disarm while reminding Israel of Lebanon's sovereignty.