The US is sending additional troops to the Middle East during a sharp spike in violence between Israel and Hezbollah forces in Lebanon that has raised the risk of a greater regional war, the Pentagon has said.

Pentagon press secretary Major General Pat Ryder would provide no details on how many additional forces or what they would be tasked to do as the announcement came on Monday.

The US currently has about 40,000 troops in the region.

Smoke rises from Israeli airstrikes on villages in the Nabatiyeh district, seen from the southern town of Marjayoun, Lebanon (Hussein Malla/AP)

The new deployments come after significant strikes by Israeli forces against targets inside Lebanon that have killed hundreds and as Israel is preparing to conduct further operations.

The State Department is warning Americans to leave Lebanon as the risk of a regional war increases.

“Due to the unpredictable nature of ongoing conflict between Hezbollah and Israel and recent explosions throughout Lebanon, including Beirut, the US Embassy urges US citizens to depart Lebanon while commercial options still remain available,” the State Department cautioned on Saturday.