There have been quite a few murderous attacks on People and magazines that publish the image/cartoon of Prophet Muhammad of Islam.

Is thee any injunction in Islam to this effect?

There seems tobe no mention of this subject in the Koran.

It seems that the Sunnis are responsible for this.

*Corrections welcome.

Islam, Branches Sects

“Most Sunni Muslims believe that visual depictions of all the prophets of Islam should be prohibited^[3] and are particularly averse to visual representations of Muhammad.^[4] The key concern is that the use of images can encourage idolatry.^[5] In Shia Islam, however, images of Muhammad are quite common nowadays, even though Shia scholars historically were against such depictions.^[4][6] Still, many Muslims who take a stricter view of the supplemental traditions will sometimes challenge any depiction of Muhammad, including those created and published by non-Muslims

Thre are some Hadiths to this effect.