Turkish riot police have entered Istanbul's Taksim Square where anti-government protesters have been staging demonstrations for close to two weeks.

Hundreds of officers have been using tear gas and water canon to disperse activists.

The move comes after Prime Minister Recep Tayyip Erdogan agreed to meet the protest organisers on Wednesday.

But the BBC's Mark Lowen, who is overlooking Taksim Square, said the clashes may threaten the success of those talks.