A plain-clothes cop who allegedly fired tear gas at journalists at point-blank range during last week's anti-government rallies is the subject of an internal police probe, according to Kenyan media.

A viral video which appears to show the officer breaking a windscreen and firing tear gas at journalists inside a car drew condemnation from diplomats and politicians.

The car was part of a convoy accompanying opposition leader Raila Odinga as he made his way through neighbourhoods in Nairobi to rally supporters.

On Tuesday the Inspector General of Police Japheth Koome said that all alleged incidents of police misconduct during the protests were being probed.

"A policeman breaking a window of the car? Regarding all officers, any issue of malpractice or misconduct brought to us is investigated and we take action. I received those complaints and they are being handled," he is quoted as saying by The Star news website.