In Ankara, Turkey's capital, about 5,000 people shouted "killer Israel" during an anti-Israeli rally as anger mounted in a country traditionally considered an ally of Israel.
The demonstration is the second largest in Turkey in as many days.
The protesters, who turned out in freezing weather, shouted "resist and win freedom" in support of Hamas.
Many waved Palestinian flags and wore headbands with Arabic scripts.
The fighting has troubled Turkey's efforts to help broker peace between Israel and its Arab opponents, forcing Turkey to suspend its mediation between Israel and Syria and leading to resignations by some of Turkey's politicians from a Turkish-Israeli friendship group.
In Britain, about 18 protests across the country, the largest being held in London, are expected to draw up to 20,000 during the day.
Nadim Baba, Al Jazeera's correspondent in the British capital, said protest organisers were expecting a big turnout.
On Friday, riot police clashed with protesters in Jerusalem and in the Jordanian capital Amman, firing teargas to push back hundreds of demonstrators marching towards the Israeli embassy. Several protesters were beaten and arrested by police.
More than 10,000 people marched through Indonesia's capital carrying banners and Palestinian flags.
The demonstrators gathered in the city centre to pray for the
safety of Palestinians before marching to the US embassy, which was guarded by hundreds of police.
Protests were also held in other Indonesian cities after Friday prayers.
|People shouted anti-Israel slogans
during a rally in Moscow [EPA]
In Egypt, the Muslim Brotherhood called for marches nationwide. Hundreds of riot police were deployed around key mosques in Cairo in anticipation of the protests.
Egyptian police also detained 40 members of the Muslim Brotherhood, security officials said.
Thousands of people were out in Istanbul to support the Palestinians and show their outrage at Israel.
In Australia, more than 4,000 people gathered in the Parry Park in Sydney.
Five local mosques had closed, asking worshippers to attend the vigil instead of the traditional Friday prayers.
Ibrahim Abu Mohammad, a local imam, led the service, urging Israel to recognise a humanitarian crisis in Gaza and agree to a ceasefire.
"Israel is committing an act of terrorism. It's the duty of all the free people in the world to stand against it and stop this evil," he said.
Hundreds took to the streets of the Bangladesh capital Dhaka after the Friday prayers and in the Philippines, dozens of demonstrators gathered in Manila, accusing Israel of war crimes.
In the Pakistani capital Islamabad, demonstrators called on the Arab and Muslim world to stop what they called the massacre committed against the population of Gaza.