(Adds latest report showing fewer roadblocks)
By Caroline Stauffer
SAO PAULO, March 1 (Reuters) - Brazilian police cracked down on striking truckers on Sunday, arresting protesters and ending roadblocks in all but two states after demonstrations turned violent and slowed food deliveries in Latin America's largest economy.
By Sunday evening, there were only 12 partial roadblocks nationwide, down from 52 on Saturday, the federal highway police said in a report on the 12th consecutive day of strikes over rising freight costs.
Authorities in the southern state of Rio Grande do Sul detained at least eight people and sent riot police to some areas, ending blockades in a state that erupted in violence over the weekend.
Protesters torched a vehicle full of tires overnight, police said, after protester Cléber Adriano Machado Ouriques was hit and killed by a truck that did not stop at a blockade in the municipality of São Sepé.
The nearly 2-week-old movement has slowed grain deliveries, forced meat-processing plants to close and started to leave some grocery stores with bare shelves.
Two of the remaining roadblocks were on the BR 163 highway in Brazil's top soy-growing state of Mato Grosso and the other 10 were in the southern state of Santa Catarina, where protesters have periodically blocked access to Brazil's main poultry-exporting port of Itajai.
The federal government vowed late on Saturday to increase the police presence on affected highways and end the roadblocks. Police started handing out steep fines last week to those blocking roads illegally.
Protest leaders say the government has still not adequately addressed their concerns over high fuel and freight costs.
The country's No. 2 and 3 soy-exporting ports of Paranagua and Rio Grande had warned that dwindling soy stocks at the ports could affect exports if roadblocks continued.
The main grains-exporting port of Santos has operated normally for the past week, although protesters briefly moved onto a major highway on Sunday in the state of Sao Paulo where the port is located. (Reporting by Caroline Stauffer; Editing by Meredith Mazzilli and Peter Cooney)