Protesters burned Israeli flags in Sweden and threw shoes at the U.S. consulate in Edinburgh, Scotland. In central London, three officers were hurt when demonstrators hurled shoes and placards at police outside the Israeli Embassy. One officer was knocked unconscious. Some 180 people were arrested in Paris.
A crowd of 12,000 gathered in London's Hyde Park carrying placards marked "Gaza: Stop the massacre" and chanting "free, free Palestine."
Police said 15 people were arrested after a group of around 2,000 demonstrators clashed with police guarding the Israeli embassy. Two were detained on suspicion of assaulting police officers.
Scores of marches were held across France, the biggest of them in the capital, where police estimated 30,000 people took part. Paris police scuffled with a small group toward the end. Police said they made 180 arrests and a dozen police officers were injured.
Police estimated that 30,000 people protested in the northern Spanish city of Barcelona, some carrying bloodstained blankets and mock dead bodies of children.
The demonstration had been called by around 300 Catalan groups who have asked the Spanish government to back cease-fire initiatives and to stop all trade, especially arms, with Israel.
In Italy, several thousand people carrying Palestinian flags marched in Milan, Florence and Venice to protest the Israeli offensive. In Milan, protesters burned a white sheet with the Star of David on it, and some participants carried posters with the Israeli flag and a swastika on them, the ANSA news agency reported.
In Germany, some 8,500 people rallied in Berlin's Alexanderplatz and then marched to the city's main train station. Hundreds of police were deployed along the route, and several Hamas flags were confiscated from the protesters. No serious incidents were reported, however, police said.
In the western German city of Duisburg, 10,000 people marched.
Nearly 20,000 people marched through the southern Lebanese town of Nabatiyeh in a protest organized by the militant Hezbollah group, a strong ally of Hamas that fought its own war with Israel in the summer of 2006.
In Norway, police used tear gas to try to disperse at least 1,000 protesters after some hurled bottles, rocks and fired fireworks at officers. Two people were injured and two were taken into custody, said Oslo police spokeswoman Unni Groendal.
Protesters in Sweden tried to break through sealed-off areas at Israel's embassy in Stockholm after a march through the city by 3,000 to 5,000 people.
Pro-Palestinian demonstrators in Athens were joined by several Greek leftist groups to form a crowd of about 2,000 who marched to the Israeli Embassy.
Thousands of anti-Israel protest In Indonesia and Malaysia ended up with flag-burning.
On Friday, more than 60 people were injured during a large demonstration in Algeria's capital, many by stone throwing, the Interior Ministry said. One journalist was left in a coma.