MADRID (AFP) - Cities around the world staged fresh protests Sunday both in support of and opposed to Israel's attacks on the Gaza Strip as the bombing campaign entered its third week. Thousands of students, trade unionists and politicians marched through the centre of Madrid to denounce the Israeli action in Gaza and call for peace. Protesters marched between the Plaza de Cibeles and Puerta del Sol, brandishing placards that read "Stop the genocide in Palestine" and "We are all Palestinians." Some members of the crowd wore Palestinian flags to show their solidarity with the people of Gaza. In Brussels, Muslim associations, centre-left politicians and pressure groups began their own rally to call for a halt to the conflict. Organisers said they estimated between 10,000 and 15,000 people would attend. Around 4,000 people marched through the western Austrian town of Bregenz, despite the extremely cold weather, organisers said. The demonstrators, including families with children, waved Turkish, Palestinian and Arab flags, played music and carried signs with slogans like "Let Gaza live". Some wore T-shirts that said, "We are all Palestinians". Jewish groups across Europe also held rallies in support of Israel and denouncing Hamas. Thousands of British Jews rallied in central London to call for peace for the citizens of both Israel and Gaza. Waving Israeli and British flags and carrying anti-Hamas placards, demonstrators prayed for peace as speakers demanded Hamas stop firing rockets at Israeli civilians. Henry Grunwald, president of the Board of Deputies of British Jews, the Israeli ambassador Ron Prosor, Chief Rabbi Jonathan Sacks and lawmakers addressed the demonstrators, who chanted: "Yes to peace". Police estimated the crowd at the demonstration in Trafalgar Square at 4,000, but organisers claimed the turnout was closer to 20,000. Counter-demonstrators lining the side of the square chanted throughout the rally, waving placards reading "We are all Hamas. Boycott Israel", "Israeli terrorist cowards" and "End the siege " talk to Hamas". Police in Marseille, southern France, said around 4,000 people marched through the city in support of Israel's right to self-defence. Outside of Europe, pro-Palestinian rallies were also held across Asia earlier Sunday. In Hong Kong, more than 1,000 students and ethnic minorities took part in a protest organised on social networking website Facebook. The group, holding placards and banners, marched from Victoria Park to the US consulate general demanding the United States stop supporting Israel's offensive on Gaza. In Indonesia, 20,000 Muslims staged a peaceful rally Sunday in the capital of Jakarta. Protesters from the Islamic Prosperous Justice Party (PKS) gathered at the national monument in Jakarta and marched through the streets. In London, angry demonstrators hurled sticks and stones at police outside the Israeli embassy as officers in riot gear and on horseback charged the crowd to keep them away from the building in the upmarket Kensington district. In Paris, protesters smashed shop windows in central Paris and threw bottles at riot police, who fired tear gas in response.