Paris's Louvre museum was closed on Wednesday due to a walkout by some staff over a rise in aggressive pickpockets including children sometimes working in gangs of up to 30, staff and management said. Disappointed tourists waited in vain in front of the famed museum, home to works of art such as the Mona Lisa and Venus de Milo, which receives some 10 million visitors a year. Christelle Guyader of the SUD union said staff had staged the walkout as they were fed up with dealing with the often-violent thieves. "Sometimes they come to work afraid because they find themselves confronted with organised groups of pickpockets who are increasingly aggressive and which include children, who get into the museum free and even when taken in for questioning by police, come back a few days later," she said. Numerous staff had reported "spitting, insults, threats and being struck", by the pickpockets and had repeatedly reported the incidents, Guyader said. The museum -- one of the world's largest and most-visited -- said it lodged a complaint with prosecutors late last year over the problem and demanded a greater police presence. "Two hundred staff exercised their right to walk off the job on Wednesday," a museum spokesperson told AFP. About 100 staff later gathered in front of the Ministry of Culture where a delegation was received. Monika Kreuzig, an Austrian teacher accompanying a group of pupils on a visit to the gallery, said they had waited in front of the Louvre's glass pyramid for over an hour. She told AFP she was "very disappointed" as her group might not be able to return as they had to leave the city within days. Staff said the pickpockets were often children from eastern Europe operating in gangs of up to 30. "There are always pickpockets at the Louvre and other tourist hotspots in central Paris, but for a year and a half they have been more and more violent... and their way of working well organised," said staff member Sophie Aguirre, also of the SUD union. The museum's management told AFP it would from now on impose temporary restrictions on entry to the museum for anyone already identified as a pickpocket. It was not yet clear when the museum would reopen. Some 150 individual complaints had been included in the management's complaint to the prosecuting authorities, it added. The Louvre has around 1,000 staff with some 470 present on any one day. The situation is a blow to the image of the French capital following a number of incidents involving Chinese tourists. On March 20, a group of 23 Chinese tourists who had just arrived in the country, was targeted outside a restaurant at Le Bourget, north of Paris. Their guide was attacked and had a bag containing passports and a large sum of cash stolen.