RMT, the UK’s largest transport union, is demanding better pay and shorter working hours.

Members of the United Kingdom’s largest transport union have gone on strike in London, bringing the city’s underground train system to a halt as tube services are suspended.

The National Union of Rail, Maritime and Transport Workers (RMT) said about 10,000 members walked off their jobs on Sunday night for the first of five days of strikes over working hours and pay.

The London Underground, which carries an estimated 5 million people daily, showed on its website that all of the capital city’s underground tube lines were either suspended or partially suspended with the exception of the newly built Elizabeth Line, which took the strain of commuters seeking alternative paths into the city. The Transport for London (TfL) website crashed due to increased web traffic.

Queues formed outside Elizabeth Line stations, and platforms in the city were crowded. The rest of London’s transport system and national rail services were unaffected by the strike.

The BBC showed an image from the Neasden train depot in northwest London showing dozens of stationary tube carriages.

RMT members took positions on picket lines across tube stations in London as part of the industrial action, which began on Sunday at 6pm (17:00 GMT) and will continue until Thursday.

The transport union decided to take strike action after it rejected an annual pay increase of 3.4 percent from TfL, which is the public body responsible for operating London’s buses, underground and other transport services. RMT is also pushing for reduced working hours from 35 to 32 hours a week.

An RMT spokesperson said: “We are not going on strike to disrupt small businesses or the public. This strike is going ahead because of the intransigent approach of TfL management and their refusal to even consider a small reduction in the working week in order to help reduce fatigue and the ill-health effects of long-term shift work on our members.”

In a post on X, RMT said the tube was operating with 2,000 fewer staff than before the pandemic, which was resulting in “extreme shifts (4 am starts, 1 am finishes) to keep London moving.” The post added: “Fatigue and understaffing are a dangerous mix.”

Kim Johnson, a left-wing MP for Liverpool, showed support for the RMT members and said on social media: “No worker should be put at risk by fatigue & extreme shift rotations”.

TfL says any reduction in hours is “unaffordable and impractical”.

In a post on X, London Mayor Sadiq Khan called on TfL and RMT “to get around the table and resolve their dispute”. He added: “Nobody wants to see strike action – it causes serious disruption for Londoners, businesses and visitors alike.”

No talks are currently scheduled between RMT and TfL. Their last round of talks collapsed on Wednesday.