Police barricade Istanbul's main square By Ivan Watson and Gul Tuysuz., CNN July 6, 2013 -- Updated 1814 GMT (0214 HKT) Turkish riot police fire a water cannon at protestors during an anti-government protest at Taksim Square in Istanbul, Turkey, on Saturday, July 6. NEW: Government won't allow "illegal" gatherings, interior minister says Witnesses reported use of water cannons and tear gas CNN witnessed several men being detained by police Court overruled parts of Taksim development project, including plans to rebuild barracks Istanbul (CNN) -- Police barricaded Istanbul's main Taksim Square and used water cannons to disperse crowds on Saturday to prevent demonstrators from entering Gezi Park, the site of protests for more than a month. Interior Minister Muammer Guler said the government won't permit "illegal" demonstrations in the park. "We will not and cannot permit demonstration or marches in those places," the minister said. Without it being a demonstration or a protest march, they can use Gezi Park as they please. We will not allow tents. Right now in Istanbul there is a search and a push for ways to have illegal gatherings. Our police is not permitting this," Guler said. Witnesses who spoke to CNN by phone reported use of water cannons and tear gas on Istiklal Street, one of the main arteries leading to Taksim square. "They are in the smaller streets trying to prevent people from even reaching Istiklal," said Irem Koker, an eyewitness. CNN witnessed several men being detained by police. One demonstrators said "this is a police state," as water cannons were being used to disperse the crowd. The 6th Administrative Court in Istanbul overruled some parts of the Taksim development project, including plans to rebuild old barracks in Gezi Park. Taksim Solidarity, an umbrella platform of activists and civil society groups, put out a call after ruling for people to gather in Gezi Park, which has not been open to the public since June 16. European Union, Turkey avoid rupture in relations "We are going to our park to deliver the court decision by hand, which cancels the project aimed to disidentify, depopulate and concretize Gezi Park, to the ones who shut the park down to the people," said Taksim Solidarity in a written statement. We are going to our park to open its doors to its real owners, so to everyone again. The Istanbul governor said that Gezi Park will open to the public Sunday but that Taksim Solidarity's call for a demonstration is not legal and will not be permitted. It is not legal to gather in Taksim. I cannot let you gather where the law says you cannot," Istanbul Gov. Huseyin Avni Mutlu told reporters on Saturday. We are not going to allow this illegal gathering. The police will make the necessary warnings," he said.