Rail, Maritime and Transport Union (RMT) members began a 48-hour strike in London at 6:59 p.m. local time in a dispute over pay and proposed job cuts.
The BBC is reporting that extra transport services have been laid in London as the Tube strike goes into effect. There will be 100 extra buses, extra river services, escorted cycle rides into central London and extra bike parking, Transport for London said.
Normal Tube services are not expected to resume until Friday morning.
The strike, expected to affect all lines, was triggered following an RMT ballot last month that saw 2,810 members voting for the walk-out while 488 voted against it.