More than 20 security officers were injured in the confrontation as police clashed with the protesters who threw sticks and stones.
The demonstrators were stopped just in front of the entrance to the chamber of deputies in a scuffle that was broadcast live on television.
Brazilian President Luiz Inacio Lula da Silva promptly condemned the incident and accused demonstrators of "committing a serious act of vandalism against the parliament."
The president's spokesman, Andre Singer, said Lula expressed his "solidarity and support to the national Congress" and that he was sure social movements in Brazil did not identify with the demonstrators.
The protesters, from a radical group that has split from the larger
Landless Workers' Movement said they had planned to present a letter to the parliamentary speakers in a peaceful manner but had reacted to what they called aggressive measures by security officers.
"It was a peaceful action but the police attacked us," protest leader Burno Maranhao told reporters.
Organisers said they were demanding the government carry out land reform and release more than four billion dollars set aside for agricultural assistance. The movement of landless peasants seeks government help in expropriating fallow land for their use.
The incident sparked an intense debate in the chamber, with opposition deputies charging that corruption allegations surrounding Lula's ruling coalition had undermined the public's confidence in government.