US marines are being issued with rifle sights carrying thinly-veiled references to Bible passages, it has been disclosed.

Troops deployed in Iraq and Afghanistan are firing weapons with coded inscriptions including 2COR4:6 and JN8:12, which relate to verses in the books of Second Corinthians and John respectively.

The secret markings do not sit comfortably US government rules forbidding its forces from spreading any religious faith during deployments to the two Islamic-majority countries.

The branded equipment was produced by the Michigan-based manufacturer Trijicon, which has a contract to supply more than 800,000 sights to the US marines and other branches of the military.

The firm confirmed to ABC News that the small inscriptions – which are about the same size as the product code on the sights – relate to New Testament passages.

The company was founded by devout Christian Glyn Bindon, and its website carries pledges to live up to the "Biblical standards" that it says made America great.