The strike will not affect refined oil-product shipments by the Port of St Petersburg, a separate company.
It is, however, likely to disrupt exports of steel from Severstal (CHMF.MM: Quote, Profile, Research), aluminium from United Company RUSAL and coal mined in western Siberia. Copper, zinc and nickel exports through the port will also be affected.
Alexander Moiseyenko, head of the Sea Port's trade union, told Reuters workers had gone on strike after their demand for a 30 percent wage increase was rejected.
"Work has stopped due to terms and conditions," he said. "Dockers and workers are working for an hour at the beginning of each shift and the same at the end of each shift."
Moiseyenko said workers would continue the strike until their wage demands were accepted.
Booming inflation in Russia, where consumer prices are now expected to rise more than 10 percent in 2007, has prompted strikes over pay and conditions in the transport sector. Workers at Ford Motor Co's plant near St Petersburg launched a one-day strike last week over pay.
The Sea Port of St Petersburg said in a statement that exports were likely to fall, but that it would not meet dockers' demands. "The trade union has not given us an economic explanation of their demand," the sea port said in the statement, adding that it considered the strike action "populist".
Lisin, the port's owner, is the majority owner of Novolipetsk Steel , Russia's fourth-largest steel maker.
Dockers at the smaller of St Petersburg's port operators last went on strike in 2005, causing a decline in export cargoes.
The port authority says the average wage for dockers in St Petersburg is over 33,000 roubles ($1,332) per month. In Tuapse on the Black Sea, the average wage is over 35,000 roubles.