The Eiffel Tower, one of the world's top tourist attractions, was closed Monday after staff went on strike, unions told AFP.
The strike, which was called to protest over the way the monument is managed financially, could be extended, they said.
The tower's operator, SETE, said on its website that "visits of the monument will be disrupted on Monday".
It advised ticket holders to check its website before showing up, or to postpone their visit. E-ticket holders were asked to check their e-mails for further information.
The stoppage is the second strike at the Eiffel Tower within two months for the same reason.
Unions have criticised operator SETE for its business model that they say is based on an inflated estimate of future visitor numbers, while under-estimating construction costs. The Eiffel Tower -- Paris's most famous landmark -- attracts nearly seven million visitors a year, around three-quarters of them foreigners, according to its website.