Police reinforcements were deployed in Bulawayo, the second largest city in the country, where shops and banks were closed, state radio reported.
Major supermarkets and many other stores in Bulawayo did not open Wednesday because people did not show up for work, store owners said.
Factory owners in Harare reported fewer workers showing up at their jobs Wednesday.
"Those who have made it say the buses are harder to get today. Some have walked to work," said Amos Chimedza, a furniture factory supervisor in the Southerton industrial district.
He said with about 60 percent absenteeism, many businesses sent workers home and closed their gates.
"We can't operate like this. It's as quiet as a Sunday round here," said Chimedza.
The government has yet to comment on the strike action.
The two-day strike which began Tuesday and a series of demonstrations in outlying townships were called by the main opposition Movement for Democratic Change to protest alleged government repression and acute shortages of food and gasoline.
In clandestinely distributed fliers, the opposition called for peaceful protests carried out with "utmost discipline".
"People must demand change through action if we are to survive in these trying times," the fliers said.
Police said 53 people were arrested in sporadic violence Tuesday in impoverished townships surrounding Harare, the capital.
Two buses and a truck were torched by rioters Tuesday, police said. They fired tear gas in eastern Harare where they said gangs of youths hurled stones at passing cars and attempted to block streets surrounding a bus station.
A van of the state Zimbabwe Broadcasting Corp. was damaged in a stoning attack and a bakery truck was intercepted and looted.
Police spokesman Wayne Bvudzijena said detectives were investigating what he described as "ringleaders who are paying youths to participate in illegal activities."
Army units were deployed in some neighborhoods of Harare and imposed an informal curfew in one district, telling people to keep off the streets.
Despite the violence, there were no immediate reports of widespread injuries. Police said one man received serious head injuries in clashes in western Harare.
The response to the call for "mass action" was the largest since President Robert Mugabe was re-elected last year. The election was denounced by the opposition after international observers said it was swayed by intimidation and rigging.
The opposition hoped the action would paralyze the economy and force Mugabe to step down ahead of new internationally supervised elections, said spokesman, Paul Themba Nyathi
Zimbabwe began to destabilize three years ago when the government launched an often violent campaign to confiscate 95 percent of white-owned farmland as part of its land reform program. [End]
(as-sv-dk-scl)
One small step...
And enormous courage.