Italy's government has said Fiat must commit to keeping all five of its car plants in Italy if it goes ahead with an Opel takeover, media reports said on Tuesday.

"Keeping the five Fiat plants in Italy is indispensable," economic development minister Claudio Scajola told Italian news agencies, according to AFP.

Fiat workers have been reported widely fear plant closures in Italy if the group takes control of Opel.

Workers staged a demonstration last Saturday in the northern city of Turin, Fiat's home town, to demand guarantees that plants in Italy would be maintained.

Fiat's plans have also unnerved Opel workers who have predicted possible job cuts and plant closures in Germany, Italy, Belgium and Britain.

Fiat boss Sergio Marchionne on Tuesday met in Frankfurt with the head of the powerful IG Metall union, which is firmly opposed to a Fiat takeover of Opel.

A union spokeswoman later told AFP Marchionne had asked for the meeting, adding that the items covered would remain confidential.

Marchionne on Friday said he would do his best "to guarantee the greatest number of jobs in Italy" and pledged to confer with government and labour representatives once his takeover talks with Opel are completed, the news agency noted.