One photograph to be published in the Saturday editions of the Daily Mirror newspaper shows a British soldier urinating on a hooded Iraqi prisoner.
UK army chief General Sir Mike Jackson ordered the probe after it emerged that the newspaper was to publish the photos.
"I am aware of the allegations which have been made today of abuse of prisoners by British soldiers in Iraq," Jackson said in a statement on Friday.
"The allegations are already under investigation. If proven not only is such appalling conduct clearly unlawful it clearly contravenes the British army's high standards," Jackson said.
"If proven the perpetrators are not fit to wear the queen's uniform. They have besmirched the good name of the army and its honour," he added.
The British probe comes just a day after photos of US soldiers abusing Iraqi captives held in a Baghdad prison surfaced, drawing international condemnation.
According to the Daily Mirror tabloid, the prisoner was allegedly threatened with execution during an eight-hour ordeal, which left him bleeding and vomiting, with a broken jaw and smashed teeth.
The newspaper said it was given the pictures by serving soldiers from the Queen's Lancashire Regiment, who were horrified by the act depicted and concerned that ''rogue elements'' in the army were undermining efforts to win Iraqi hearts and minds.
Speaking on condition of anonymity, the soldiers told the newspaper the unnamed captive - against whom no charges were brought - was driven away and dumped from the back of a moving vehicle after the ordeal.
It was not known whether he survived, they said, according to the Daily Mirror.