* Nissan recalled 1.2 mln Japan-sold cars
* Recall comes after improper practices during final checks
* Certified technicians' stamps used on final-check documents -ministry
* Nissan to file recall Friday afternoon -ministry (Adds minister comments and details)
TOKYO, Oct 6 (Reuters) - Japanese Transport Minister Keiichi Ishii said on Friday that unauthorised technicians had been found certifying vehicles at five Nissan Motor Co plants that the ministry has been inspecting.
The unauthorised technicians included contract workers, Ishii told a news conference.
"It's extremely regrettable, causing anxiety for users and shaking the foundation of the certification system," he said.
The ministry said it has carried out spot inspections at all of Nissan's six assembly plants in Japan and found stamps of certified technicians were used at five plants on documents to sign off final vehicle checks conducted by non-certified technicians.
Nissan has decided to recall all 1.2 million new passenger cars it sold in Japan over the past three years after discovering final vehicle inspections were not performed by authorised technicians.
Ishii said Nissan was expected to file the recall with the ministry on Friday afternoon. (Reporting by Maki Shiraki; Editing by Michael Perry)