An Italian artist accused of blasphemy for an "obscene" painting of Jesus was injured in a scuffle Thursday with a protester vandalising his exhibition in a Catholic church, police said.

The diocese of Carpi in northern Italy offered its full support for artist Andrea Saltini after what it condemned as an "unprecedented act of violence" ahead of the Christian holiday of Easter.

Saltini's exhibition "Gratia Plena" -- meaning "full of grace" in Latin, a line from a Catholic prayer -- had opened at the diocesan museum at the Church of Saint Ignatius on March 2.

But the paintings drew protests and 30,000 people signed a petition accusing him of blasphemy, saying one picture showed Jesus "engaged in an obscene sexual act".

On Thursday morning, a masked man carrying black spray paint and a knife entered the exhibition aiming to damage the artworks, a local police spokesman told AFP.

The artist confronted the vandal as he sought to cut one of the paintings, and was "lightly injured". He later sought hospital treatment.

The attacker got away, but police believe the injury was inflicted accidentally, with the perpetrator perhaps not even realising who Saltini was.

The diocese thanked the police for their "timely intervention" and offered its full cooperation with any investigation.

The diocese had previously rejected accusations of blasphemy, hailing Saltini's works as a rare example of "true contemporary art with a religious subject".

The paintings are inspired by Christian subjects, including the Immaculate Conception of the Virgin Mary and the crucifixion of St Peter.

But the petition declared "No to blasphemy disguised as art" and urged the withdrawal of the "profoundly disrespectful" works, alongside a blurred picture of a painting showing a man bending over the lower half of a naked Jesus.

The organisers of the petition, anti-abortion group Pro Vita, offered its "full solidarity" with Saltini after what it called a "crazy and unjustifiable attack".

Concerns about his work "cannot in any way justify any type of personal violence", Pro Vita President Antonio Brandi said in a statement.