FORTALEZA - A man was shot in the leg during clashes between rival fans outside Brazil's Castelao Arena, one of 12 stadiums to be used for this year's World Cup.

Authorities in the northeastern city of Fortaleza reported 75 arrests but were still seeking the armed assailant on Sunday night, police chief Aginaldo de Oliveira told local media.

Violent clashes also occurred inside the Castelao Arena during Ceara's 3-1 victory over Fortaleza in the Ceara state championship.

Sunday's clashes raised fresh concerns about fan safety during the World Cup, to be held from June 12 to July 13.

In February three fans were shot outside the Arena das Dunas World Cup stadium in Natal.

And in December dozens were injured in a riot during the Brazilian top-flight match between Atletico Paranaense and Vasco da Gama in the southern city of Joinville.

Castelao Arena will host six World Cup matches, including a quarterfinal on July 4.