Commuters in London are navigating traffic jams and packed pavements on their way to work as unions representing London Underground workers held a 24-hour tube strike.

Most of the capital’s tube stations have been closed since 6pm yesterday after last-minute talks failed to halt industrial action in a dispute over staffing levels and ticket office closures.

Transport for London (TfL) has warned of severe delays all day and advised people not to travel if they can avoid it.

A notice giving details of a strike involving London Underground workers at Waterloo Underground Station on Sunday (Reuters)

Why are London Underground workers on strike?

Two unions, the RMT and TSSA, say job cuts and the closure of ticket offices in recent years have left stations without enough staff to run safely.

Weekend negotiations ended without agreement, and the unions say management hasn't done enough to address staff concerns.

"Our members are out in force across London Underground this morning in the fight for jobs and safety,” said RMT general secretary Mick Cash.

"This action has been forced on us by savage cuts to jobs that have reduced London Underground to an under-staffed death trap at a time of heightened security and safety alert.”

Steve Griffiths, London Underground chief operating officer, said the transit operator has agreed to hire hundreds of new station staff.

"There is no need to strike,” he said. “We had always intended to review staffing levels and have had constructive discussions with the unions.

"We agree that we need more staff in our stations and have already started to recruit 200 extra staff."

London's Mayor Sadiq Khan criticised the industrial action and called on the unions to return to the negotiating table.

Which tube lines are down?

During the strike, there will be no Underground services from key interchange stations such as Victoria, King's Cross, Waterloo, Paddington, Euston, Bank and London Bridge.

There will be no service at all on the Victoria or Waterloo & City lines, and all other lines will be severely affected.

On a typical weekday, four million journeys are made on the London transport network.

Gallery: 150 years of London underground Show all 27 1 /27 Gallery: 150 years of London underground Gallery: 150 years of London underground tube8.jpg Passengers on the London Underground in 1955 PA Gallery: 150 years of London underground Untitled-1.jpg The London Tube is celebrating its 150th anniversary Getty Images Gallery: 150 years of London underground tube18.jpg World War II, 25th, September, 1940, Members of the public huddle together in a London underground station Getty Images Gallery: 150 years of London underground tube17.jpg Queen Elizabeth II travels on a tube train after the official opening ceremony of London Underground's Victoria Line in 1969 Getty Images Gallery: 150 years of London underground tube5.jpg A London Transport official showing the Prince of Wales the controls in the driver's car of a Jubilee Line train in 1979 PA Gallery: 150 years of London underground tube12.jpg Emergency services at Chancery Lane Underground Station in London after a tube train derailed in 2003 PA Gallery: 150 years of London underground tube1.jpg In this file picture taken on September 4, 2007 passengers jostle to enter the Underground station at Waterloo Station in central London, as commuters battled with severe transport disruption to get to work as unions staged a second day of strikes on the capital's underground system AFP Gallery: 150 years of London underground tube14.jpg Mayor of London Boris Johnson at the opening of the ticket hall at King's Cross St Pancras Station PA Gallery: 150 years of London underground tube3.jpg Londoners take shelter in the London Underground during the Blitz PA Gallery: 150 years of London underground tube4.jpg David Cameron travelling by tube on the Underground to the O2 Arena in London PA Gallery: 150 years of London underground tube9.jpg Lord Ashfield handing over the silver key to Col. Moore Brabazon during the opening of the Northern line, London in 1926 PA Gallery: 150 years of London underground tube13.jpg Two 'buskers' entertain travellers by playing musical instruments on the London Underground in central London AFP Gallery: 150 years of London underground tube2.jpg London resident Jean Farrow, 36, one of the first directly recruited female drivers sitting at the front of a tube train at Hammersmith station PA Gallery: 150 years of London underground tube7.jpg An underground train heads into Central London on the Piccadilly Line on day of winter AFP Gallery: 150 years of London underground tube11.jpg Torchbearer and London Underground employee John Light carrying the Olympic Flame onto an underground train at Wimbledon Station, London PA Gallery: 150 years of London underground tube10.jpg The fire-damaged escalators at King's Cross underground station in London in 1987 PA Gallery: 150 years of London underground tube19.jpg London Underground workers building the Piccadilly Line extension at Turnpike Lane in 1930 Getty Images Gallery: 150 years of London underground 141007280.jpg Marble Arch Tube Station Getty Images Gallery: 150 years of London underground 141007351.jpg A commuter at Westminster Getty Images Gallery: 150 years of London underground 141007639.jpg Victorian tile signs have been updated with more modern ones in some stations Getty Images Gallery: 150 years of London underground 143711297.jpg London Mayor Boris Johnson travelling on the Tube Getty Images Gallery: 150 years of London underground 149562350.jpg Bank station during the London 2012 Olympics GettyImages Gallery: 150 years of London underground 155708342.jpg Oyster cards were introduced on the Tube in 2003 Getty Images Gallery: 150 years of London underground 155708347.jpg The entrance to Westminster Underground with Big Ben in the background Getty Images Gallery: 150 years of London underground 158719828 (1).jpg Shoppers keen to catch the Boxing Day sale queue outside Bond Street for the Tube station to open early AM Getty Images Gallery: 150 years of London underground 140839627.jpg The Tube's famously dirt-covering patterned seat fabric Getty Images Gallery: 150 years of London underground 140839693.jpg A woman at Oxford Circus station Getty Images

Are any tube lines still running?

While most stations in Zone one are closed, some lines are running with a limited service in outer London areas – for example, the Bakerloo line is operating between Marylebone and Harrow & Wealdstone.

Piccadilly line services will run between Hammersmith and Heathrow Terminals 1, 2 and 3, but there will be no service to Terminals 4 or 5.

National Rail services and London buses are not affected by the strike.

Some commuters are walking or cycling to avoid the transport chaos.