Israeli warplanes carried out late on Sept 19 their most intense strikes on south Lebanon in nearly a year of war, Lebanese security sources said, heightening the conflict between Israel and Lebanese armed group Hezbollah amid calls for restraint.

The White House said a diplomatic solution was achievable and urgent, and UK called for an immediate ceasefire between Israel and Hezbollah.

The US is "afraid and concerned about potential escalation," spokesperson Karine Jean-Pierre told a briefing.

The intense barrage followed attacks earlier in the week attributed by Lebanon and Hezbollah to Israel that blew up Hezbollah radios and pagers, killing 37 people and wounding about 3,000 in Lebanon.

In the late operation on Sept 19, Israel's military said its jets over two hours struck hundreds of multiple-rocket-launcher barrels in southern Lebanon that were set to be fired immediately towards Israel.

The bombardment included more than 52 strikes across southern Lebanon after 9pm local time (1800 GMT), Lebanon's state news agency NNA said. Three Lebanese security sources said these were the heaviest aerial strikes since the conflict began in October.