Brazilian dock workers began a one-day strike on Thursday in support of broader union demonstrations across the country, holding up 10 ships at Latin America's main port of Santos.
The stoppage also affected the ports of Rio Grande, Espírito Santo, Fortaleza, Pernambuco and São Luiz, said Wilton Barreto, president of the National Stevedores Association in Brasilia.
"This will last all day, by night everything will be back to normal," he told Reuters by telephone.
Brazil is currently exporting record soy, corn and sugar crops, and the cane harvest is peaking. Typically, bulk cargo such as grains are less affected by labor stoppages because they require fewer workers. The movement of container goods such as coffee, bagged sugar, fruits and meats is more vulnerable.
Ten of 31 ships birthed for the 7 a.m. to 1 p.m. shift at Santos were stopped. Most of them were container vessels, local port authority Codesp said in an e-mailed statement. A sugar vessel was stopped at a public terminal, although sugar exports from private terminals were apparently not affected.
Access to Santos port was blocked via two roads, preventing trucks from entering, and local media also showed protesters blocking access to Suape port in the northeast.
Analysts have said roadblocks of up to a few days were unlikely to affect exports as exporting companies keep enough supplies in private storage facilities near the ports to keep loading ships.
A spokeswoman for Brazil's No. 2 commodities port Paranagua, in the country's south, said operations were normal but workers were planning to walk off the job at 3 p.m. (1900 GMT).
The port strikes and general union marches come on the heels of a protest by truck drivers that slowed grain deliveries at major ports last week. But they have drawn smaller crowds than a nationwide popular movement that drew up to 1 million people to the streets in one of several protests in June.
Dock workers have held occasional strikes this year against legislation allowing the sale of port terminals to private companies that Congress passed on May 16. They fear a loss of jobs and benefits because private operators will no longer have to hire through the centralized agency, "OGMO."
Stevedores at Santos last held a six-hour march on Wednesday, affecting some 13 container ships, but not bulk cargo shipments such as soy and corn.
The Santos union says Embraport, a new $1.2 billion private container terminal owned by local infrastructure group Odebrecht Transport, the United Arab Emirates' DP World and trading companyCoimex, is not hiring through the OGMO.
"We are in the street protesting, in support of the day of struggle," Cesar Rodrigues Alves, a senior representative of the union of stevedores at Santos port, said.
"Tomorrow the protests will stop and we will go back to the negotiating table (with Embraport) to see what to do."
Reporting by Caroline Stauffer; Editing by Nick Zieminski, Gerald E. McCormick and Maureen Bavdek (C) Reuters 2013.