PARIS - Riot police fired tear gas in Paris on Saturday as tensions rose at a 5,000-strong pro-Palestinian rally that went ahead in defiance of a ban, days after similar rallies ended in violence.The demonstration against Israel’s Gaza offensive that has killed more than 1,000 Palestinians comes after other protests last weekend in Paris and a suburb town that had also initially been banned descended into chaos.Organisers of Saturday’s protest had tried going to court to get the ban overturned, but they were unsuccessful and Interior Minister Bernard Cazeneuve warned that they would be held “responsible for any unrest... and liable to penal sanctions. According to estimates, about 5,000 people turned up at Place de la Republique in central Paris, brandishing Palestinian flags and the red banners of the far-left New Anticapitalist Party that had called on people to defy the ban.After an initial peaceful start, police began firing tear gas after some hooded protestors threw cans and other objects at them, and several journalists were roughed up.A police source said 40 people were detained, adding that they were under strict orders to take in people who made anti-Jewish statements or gestures.Some 2,000 police were mobilised, and many of them were present on the square to stop the rally from moving on to other parts of the French capital.Moreover, at least 10,000 pro-Palestinian protesters opposed to Israel’s military action in Gaza marched through central London for the second week running on Saturday. A police source estimated the crowds at 10,000, but an AFP photographer suggested the number could be far higher, forcing the closure of roads around Britain’s parliament.The march started outside the Israeli embassy in Kensington, in the west of the British capital, before passing Downing Street and coming to a halt outside the Houses of Parliament in Westminster. Demonstrators held placards reading ‘Stop Israeli State Terror!’, ‘Freedom for Palestine’ and ‘Gaza - End the Siege.’ They also chanted ‘Shame on you David Cameron’ as they filed past the British prime minister’s Downing Street office. The crowds took over Parliament Square, where a series of speakers, including Roxy Music member Brian Eno, took to a temporary stage to call for an end to the military campaign, which has claimed more than 1,000 lives, according to official figures.“Israel clear out of Palestine, the era of settlements is over”, “Israel assassin, Hollande accomplice”, “Israel, piss off, Palestine isn’t yours” were just some of the slogans shouted by protesters.Elsewhere in the country, nearly 10,000 people turned up in the eastern city of Lyon for a similar protest, though it was not banned and went off peacefully.In the southern cities of Marseille and Nice, hundreds also turned up in support for Palestinians. The conflict has stirred up huge passions in France — home to the largest Muslim and Jewish communities in western Europe with around five million Muslims and half a million Jews.And while many protests around the country have gone smoothly, some demonstrations in Paris and the suburb town of Sarcelles have descended into chaos.In Sarcelles last weekend, Jewish businesses were looted and in one violent Paris demonstration several weeks ago, protesters tried to storm two synagogues, raising concerns among the Jewish community about anti-Semitism.But on Wednesday, several thousand people protested peacefully in Paris against the Israeli offensive, launched 19 days ago after Hamas militants fired rockets into the Jewish state.Police said the rally attracted about 14,500 people, while organisers put the figure at 25,000.