Hamas flags were held aloft at an anti-Israeli rally in Damascus
Thousands of people in the Arab world have attended rallies to express anger at Israel's air raids on the Hamas-controlled Gaza Strip.
Protesters burned Israeli and American flags in a string of Arab cities and demanded a stronger response from their leaders to Israel's "aggression".
In Egypt protests were organised by the Muslim Brotherhood, allies of Hamas.
Lebanon's Hezbollah movement, which fought a brief war with Israel in 2006, called on its fighters to be on alert.
In an address relayed to supporters in Beirut, the head of the Shia movement, Hassan Nasrallah urged those in southern Lebanon to remain vigilant in case of Israeli attacks.
"We have asked our brothers in the resistance in the south to be available and alert because we face a criminal and treacherous enemy," Nasrallah was quoted by the AFP news agency as saying.
"We are ready to face any aggression on our land, our country or our dignity," he added.
Hezbollah fought a 34-day war with Israel in 2006, in which more than 1,125 Lebanese, most of them civilians, died in Israeli attacks.
Around 160 Israelis, mostly soldiers, died in the conflict.
Big demonstrations were held in several Arab countries in response to what many in the region see as unjustified Israeli aggression against their Palestinian brothers in the Gaza Strip.
More than 50,000 demonstrated in Egyptian cities on Sunday, the AFP news agency reported.
Security officials said the biggest protest was in the southern city of Asyut.
They were led by the Islamist opposition in Egypt, the Muslim Brotherhood, the group from which Hamas first emerged.
The BBC's Christian Fraser in Cairo says the Brotherhood regards Hamas members as their spiritual brothers.
Many Palestinian emigres took part in the rallies in Lebanon, Iraq and Syria.
In the centre of the Syrian capital Damascus protesters, incensed at Israel's bombing campaign, waved green flags of the Hamas militant movement alongside Palestinian, Syrian and yellow Hezbollah flags, AFP reported.
Thousands also attended a pro-Palestinian demonstration in the Jordanian capital Amman, and there were rallies in many of Jordan's overcrowded refugee camps, home to thousands of displaced Palestinians.
There were also anti-Israeli protests in Sudan and Yemen.
A suicide bomber blew himself up at a rally in Mosul, northern Iraq, killing a protester and wounding 16.
Local police quoted by the Associated Press said the Mosul demonstration had been organised by the Sunni Iraqi Islamic Party.
"Arab silence is behind the bombings," read a banner held by one of several thousand people who turned out in the Sunni Arab city of Samarra north of Baghdad.