Most visitors to the Louvre want to see the Mona Lisa

Access to the museum was made free for visitors after strikers blocked access to ticket desks, reports say.

The Musee d'Orsay was also shut after attendants there stopped work.

Attendants are demanding a bonus they say other categories of staff have been offered, and because they suffer more stress being on the floor.

"The stress is clearly linked to the number of visitors", one Louvre attendant, who did not want to be named, told the AFP news agency.

"What's unbearable is the constant hubbub of the crowd, especially in the really popular rooms like the one with the Mona Lisa or the Venus de Milo.

"On Sundays, when the museum is free, it is even worse. There can be 65,000 visitors on one day. It's unbearable and even sometimes dangerous."

'Managing the flow'

Staff in the hall leading to the Mona Lisa - which most of the visitors to the museum want to see - said they spent much of their time reminding the public that flash photography was banned in the room where the painting was displayed.

"Sometimes you just blow your top," one staff member said.

Christelle Guyader, of the union staging the strike, said: "When the number of visitors gets so large - we had more than 7.5m in 2005 and 8.3m last year - with no increase in the number of attendants, and when more and more rooms are opened, then our work is reduced to simply managing the flow."

Management at the Louvre said that only a small percentage of the museum's attendants were on strike and that it was "having little effect", AFP reported.