The Israeli military says it has established a "forward defence line" in Lebanon and released a map showing its troops operating south of it.
The deployment has been described elsewhere as a "Yellow Line".
It says five divisions are working to dismantle Hezbollah infrastructure.
The line was not mentioned in ceasefire terms published by the United States.
Israel and Lebanon agreed to a 10-day truce, which went into effect on Thursday.
The map shows dozens of villages inside the zone, stretching several kilometres into Lebanon, whose residents would likely be prevented from returning.
There was no immediate comment from Lebanese officials but the move is likely to raise concerns in Lebanon about the scope and duration of Israel's military presence.