Hundreds of firefighters hosed down riot police and the prime minister's office in Brussels in a protest over retirement plans.

The firefighters want to keep their early retirement age at 58, arguing their arduous job does not allow them to work into their 60s.

But the government wants to raise the Belgian retirement age to 67 so it can afford an ever-increasing pension bill.

Deputy prime minister Didier Reynders said caving in to the firefighters' demands would "send the wrong signal" to everyone.