LONDON — Large swathes of London's sprawling transport network shut down Monday night after maintenance workers walked off the job, arousing commuter anger and drawing warnings the strike will inconvenience millions of Britons.

Around 2,300 members of the National Union of Rail, Maritime and Transport Workers left their jobs at 6 p.m. to begin a 72-hour strike, in a dispute stemming from the collapse of their employer, maintenance consortium Metronet.

Many commuters were caught en route home when the strike took effect, forcing them to take overcrowded buses and taxis. London Underground urged passengers to walk if possible.

Metronet's workers maintain tracks, trains and signals, and have demanded assurances that their jobs would be protected.