Twenty-three security officers were injured in the hour-long confrontation in the capital, Brasilia, authorities said.
Protesters broke open the glass doors in the parliament building with stones, sticks and a small Fiat car as a battering ram.
The demonstrators were stopped in front of the entrance to the chamber of deputies in a scuffle that was broadcast live on television.
Hundreds of demonstrators were detained, the police department said without providing precise numbers
The president, Luiz Inacio Lula da Silva, condemned the protest and accused demonstrators of "committing a serious act of vandalism against the parliament."
The president's spokesman, Andre Singer, said that 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.
'Police attacked us'
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.
Protesters overturn a car at the
entrance of the congress in Brasilia
"It was a peaceful action but the police attacked us," protest leader Burno Maranhao told reporters.
Organisers said they were demanding the government should carry out land reform and release more than $4 billion set aside for agricultural assistance.
The movement of landless peasants seeks government help in expropriating fallow land for their use.
Under Brazil's 1988 constitution, unproductive land may be expropriated as long as the owner is compensated.
The incident caused 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.