Israel's army said it was on "very, very high alert" at its border with Lebanon as the leader of the Islamist group Hezbollah broke his silence on the war.
In a speech watched by thousands at a Beirut rally, Hassan Nasrallah praised the Hamas attacks on Israel on 7 October, but said they were "100% Palestinian".
Hezbollah - which is backed by Iran and considered a terrorist group in the UK and US - has been intensifying attacks on northern Israel from Lebanon.
Israel has warned of "unimaginable" consequences if Hezbollah joins the Israel-Gaza war.
Meanwhile, the US secretary of state called for civilians in Gaza to be protected, saying he had discussed "humanitarian pauses" with Israeli leaders in Tel Aviv.
Antony Blinken will also visit Jordan as he seeks to avert an escalation of the war.
About 100 British nationals are on the list of people approved to leave Gaza today; The family of Scotland's First Minister Humza Yousaf have just been allowed out.
The Hamas-run health ministry in Gaza says more than 9,000 people have been killed in the Strip since 7 October.
Israel began bombing Gaza after Hamas killed more than 1,400 people in Israel and kidnapped more than 200 others.
