Updated

French riot police clashed Tuesday with striking train workers, who hurled bottles and blocked traffic in anger over a bill to reform the state-run railway system.

A weeklong strike by rail workers has caused some of the worst disruption to the country's rail network in years — and is heating up as the reform bill goes to the lower house of Parliament for debate Tuesday.

The bill would unite the SNCF train operator with the RFF railway network, which would pave the way to opening up railways to competition. Workers fear the reform will mean job losses and security concerns. The government says the reform is needed to create a stronger structure for the railways, as France and other European countries gear up for full-scale railway liberalization in coming years.

Several hundred workers staged a protest Tuesday near the National Assembly on Paris' Left Bank, waving red union flags and demanding that the bill be delayed or changed.

The protesters blocked cars and tried to push past police to approach the parliament building, firing flares and throwing bottles. Officers responded with tear gas and batons and wrestled a few protesters to the ground. The protesters retreated and their demonstration continued peacefully.

Later Tuesday, French television showed footage of protesters marching onto train tracks at Paris' busy Montparnasse station, which links travelers with cities across western and southwest France.

The strike began last Wednesday, and while only a minority of workers are taking part, it has disrupted travel on trains across France and on commuter lines. About a third of trains were canceled nationwide Tuesday. The strike has not affected international lines such as the Eurostar train from Paris to London, but it has caused problems for international travelers using the commuter rail to and from Paris' Charles de Gaulle Airport.

Prime Minister Manuel Valls broke with the tradition that governments don't meddle in strikes, saying Monday that the movement was "not useful and not responsible."

Lawmakers begin debating the bill Tuesday afternoon.