Israel's attorney-general has ordered police to open a criminal investigation in two unspecified matters involving Prime Minister Benjamin Netanyahu, Israel's Channel 10 television said on Wednesday.

A Justice Ministry spokeswoman said in a statement that checks in the matter "are still ongoing and this is neither confirmation or denial of what has been alleged".

"The attorney-general, the police and prosecutors are working in close cooperation and a public announcement will be made in due course about the investigation," she said.

There was no immediate response from Netanyahu's office to a Reuters query on the report.

Netanyahu has in the past denied wrongdoing in the purchase of submarines from Germany, where media have reported a potential conflict of interest involving his lawyer.

The Channel 10 report said Attorney-General Avihai Mandelblit had authorised police to question Netanyahu under caution, and that a date for the interrogation would be set in the coming days.

It said the more serious of the two cases that Mandelblit had been examining had not yet leaked out to the public.