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BRUSSELS (Reuters) - More than 60,000 unionized workers marched on Tuesday in protest against proposed Belgian labor-market reforms including longer hours and a higher retirement age, snarling up traffic in a large part of Brussels.

Police said 20 people were injured in clashes when protesters threw rocks and firecrackers at riot police, who responded by firing water cannon. Police arrested 23 people, a spokeswoman said.

The protests are the first in a series of actions planned for the coming months, including a strike on June 24 and a day of national demonstrations on Oct. 7, marking two years since the center-right government took power. “It’s always in the same purses that they come to find money,” said Marie-Claire Legros, a protester from Grace-Hollogne in the province of Liege.

Trade union workers across a wide range of sectors are upset over proposed reforms including a planned wage hike that was scrapped, higher VAT on electricity, a retirement age of 67 and extending the maximum workweek to 45 hours from 38.

Tuesday’s march cut across the capital and caused a temporary shutdown of certain transport tunnels and train stations.