TURIN, Italy, Feb 24 (Reuters) - Fiat (FIA.MI) has extended by another three weeks a halt in production at its Termini Imerese plant in Sicily, with the plant now set to be shut from March 27 to April 12, a company source said on Tuesday.

Since last year the maker of Fiat and Alfa Romeo cars has been suspending production at its six plants in Italy for varying periods of time, sending thousands of workers home on reduced pay.

The plant closures are among a number of measures adopted by Fiat to try to keep costs under control amid falling sales in the worst crisis to hit the industry in decades.

Termini Imerese is the least productive of its plants in Italy and has been viewed by industry analysts as a likely candidate for permanent closure.

With 1,400 staff it makes one model: the Lancia Ypsilon city car.

Last week the company decided to reopen for a week its Mirafiori plant in Turin for production runs of two models, including the Alfa Romeo Mito hatchback.

The latest news was not welcomed by Roberto Mastrosimone, who represents the Fiom union at Termini Imerese.

It seems like they are playing with us, he was quoted by the Ansa news agency as saying. First they announce a reduction in the period of (production halts), then they say that they will do it for another three weeks.

Italy's government has put together a package of incentives to encourage drivers to buy new cars and industry representatives have noted a rise in sales as a result. (Reporting by Gianni Montani; Editing by Greg Mahlich)