Dozens of public sector workers took the latest visit by FIFA secretary-general Jerome Valcke to the central city of Cuiaba as an opportunity to protest and demand a wage hike on Tuesday.

The group, including teachers and postal workers and backed by students, invaded the pitch at the Arena Pantanal, one of the 12 venues that will host World Cup matches next year.

Brazilian broadcaster Globo showed the 50-strong group booing as Valcke continued his latest visit to the host nation ahead of a visit to organizers in Rio on Thursday.

A second protest marred a visit by Valcke, Brazilian Sports Minister Aldo Rebelo and local organizing committee representatives and former Brazil stars Ronaldo and Bebeto to an urban mobility project.

Valcke, confronted by banners that read "FIFA go home" and "less Cup, more education" at the stadium, said people had a democratic right to voice grievances if they so wished.

Earlier, Valcke stressed the World Cup would go ahead using all 12 venues as scheduled despite lingering doubts as to whether all would be ready by a December deadline.

"For last time. The Brazil #WorldCup WILL be played in 12 host cities, according to match schedule announced Oct 2011," Valcke tweeted, adding he had "full commitment" from local authorities that Cuiaba would be ready.