MADRID (AFP) - The father of Argentina star Lionel Messi could face 18 months in prison for fiscal fraud following a request by the Barcelona public prosecutor on Tuesday.

Messi himself, however, will not face charges after being exonerated of all accusations, with the prosecutor saying he had blindly followed his father's "instructions".

According to the charge sheet published on Tuesday, Barcelona forward Messi was not aware of the fraud committed by his father, Jorge Horacio.

The pair were accused in 2013 of defrauding the taxman out of €4.16 million (S$6.6 million) in taxes related to Messi's image rights between 2007 and 2009 through the creation of fake companies in Belize and Uruguay.

Four-time world player of the year Messi is the fourth richest sportsman in the world, according to Forbes magazine which estimates he earns US$64.7 million (S$91 million) a year.

Messi's older brother Matias, 32, was briefly detained in Argentina on Sunday after he was found with a revolver in the glove compartment of his car.

He allegedly came to blows with the arresting officers and suffered a facial injury while two police officers were also hurt in the foot and knee.

He had already been charged with illegal possession of a firearm in 2008.