Kamala Harris courted voters angered by the Gaza war while Donald Trump doubled down on violent rhetoric with a comment about journalists being shot as the tense US election campaign entered its final hours.

The Democratic vice president and the Republican former president frantically blitzed several swing states as they tried to win over the last holdouts with less than 36 hours left until polls open on Election Day on Tuesday.

Trump predicted a "landslide", while Harris told a raucous rally in must-win Michigan that "we have momentum -- it's on our side."

Thousands of Iranians rallied Sunday by the former US embassy in Tehran to mark the 1979 hostage crisis, burning American flags and ridiculing Joe Biden and Donald Trump just two days before the US presidential election.

"There's no difference between Biden and Trump, between the donkey and the elephant," said protester Saber Danaie, 23, of the animal mascots that represent the Democratic and Republican parties in the United States.

Gaza rescuers said Israeli strikes in Gaza on Sunday killed at least 30 people, as the Israeli military pursues its offensive against Hamas in the north of the Palestinian territory.

"Since dawn today, at least 17 citizens have been martyred in Israeli attacks on homes and citizens in the northern Gaza Strip," said Gaza's civil defence agency spokesman Mahmud Bassal.

Among the dead were six in the town of Beit Lahia and four in Jabalia. They included women and children, he said.

Residents of Nur Shams camp in the occupied West Bank are fearful for their future after an Israeli raid this week damaged the UN agency for Palestinian refugees office there.

The 13,000 inhabitants of the camp near the northern city of Tulkarem depend heavily on the United Nations Relief and Works Agency for Palestine Refugees.

UNRWA notably runs two schools, a clinic and sanitation services in Nur Shams.

Stunned refugees watched as workers cleared rubble from around the office, which was almost totally destroyed in an "anti-terrorist" operation on Thursday.

Israel on Sunday pressed on with its campaigns in Lebanon and Gaza, launching several deadly strikes as Prime Minister Benjamin Netanyahu visited his country's northern border.

Netanyahu's visit came after an air strike killed at least three people near the southern Lebanon city of Sidon, the Lebanese health ministry said, and as more bombs hit the country's east.

Lebanon's health ministry said three people were killed in an Israeli strike Sunday near the southern city of Sidon, as state media reported the recovery of five bodies from the flashpoint southern town of Khiam.

The health ministry said a strike on Haret Saida, a densely populated neighbourhood near Sidon, killed three people and wounded nine others more than a month into the Israel-Hezbollah war.

Iran's supreme leader vowed retaliation on Saturday for attacks by Israel, as an Israeli military official confirmed naval commandos seized a suspected Hezbollah operative in a Lebanon raid.

The World Health Organization said four children were among six people wounded in a strike on a polio vaccination centre in north Gaza, where UN agencies have spoken of "apocalyptic" conditions in the face of a blistering Israeli assault.

Hundreds of Israeli protesters in Tel Aviv voiced their frustration with the government on Saturday for failing to secure a truce deal to bring the remaining hostages in Gaza home.

Flag-waving demonstrators in the country's commercial hub held placards with slogans including "Deal now", "Stop the war" and "We won't abandon them", and beat drums and chanted: "Why are they still in Gaza?"

"There have been countless opportunities to end this crisis and each one was torpedoed by the government," said demonstrator Zahiro Shahar Mor, a 52-year-old bank employee from Tel Aviv.

The World Health Organization said four children were among six people wounded Saturday in a strike on a polio vaccination centre in northern Gaza.

The WHO only restarted the second round of vaccinations in northern Gaza on Saturday after being forced to suspend them earlier because of Israeli bombardments.

WHO chief Tedros Adhanom Ghebreyesus said the health centre was "in an area where a humanitarian pause was agreed to allow vaccination to proceed" and the attack could off parents of children needing a second vaccine to be covered.

Israeli naval commandos have seized a trainee mariner a military official described as a "senior operative" of Hezbollah in a raid in Lebanon and brought him to Israel for questioning.

Lebanese Prime Minister Najib Mikati instructed the foreign ministry to submit a complaint to the UN Security Council over the raid on the coastal town of Batroun, his office said on Saturday.

The Lebanese army and UN peacekeeping force UNIFIL are both conducting investigations into the raid, Mikati's office said, adding that he had called for "expedited" results.