Evan Mawarire, a Harare pastor who rose to prominence as a critic of former leader Robert Mugabe, was bundled into the back seat of a truck by about a dozen police. He was to be charged with inciting public violence, said lawyer Beatrice Mtetwa, who witnessed the arrest along with a Reuters cameraman.
Wednesday is the third and final day of stay-at-home protests called by unions in response to the steep hike in fuel prices, which was decreed by President Emmerson Mnangagwa. Three people including a police officer died on Monday during violent demonstrations.
Mawarire, who led a national shutdown in 2016, told Reuters police had surrounded his house after he used Facebook posts to urge Zimbabweans to heed the unions' calls.
Shops, banks and fast-food chains in the capital stayed closed on Wednesday, along with some government offices, and there was no public transport and little other road traffic.
In central Harare, police fired tear gas to disperse a crowd queuing for bread at a shopping centre, a Reuters witness said. Soldiers were controlling a disorderly queue at the only shop that was open.
Many Zimbabweans accuse Mnangagwa of failing to live up to pre-election pledges to kick-start economic growth and make a clean break with the strong-arm rule of Mugabe, who was forced out in November 2017 after 37 years in power.
Since then, the country has seen a familiar pattern of dollar shortages battering the economy, rocketing inflation that is destroying the value of their savings and the government reacting forcefully to crush dissent.
The government has blamed the protests on the main opposition and local rights groups, calling it part of a plot to overthrow Mnangagwa's administration.
Mawarire rose to prominence in 2016 when he launched a social media movement - #ThisFlag - to encourage Zimbabweans to speak out against Mugabe policies the pastor blamed for high unemployment, widespread corruption and delays in getting salaries.
He was acquitted in 2017 on charges of public violence and disorderly conduct.
Econet Wireless Zimbabwe, the country's largest mobile operator, said its internet services had been cut off following an order from the government.
"We are obliged to act when directed to do so and the matter is beyond our control," Econet said in a text message to customers, adding that all networks and providers had suspended their services.
Internet services were cut by mid-morning on Tuesday, leaving many people without access to social media platforms amid accusations that the government wanted to prevent images of its heavy-handedness from being broadcast around the world.
Information Minister Monica Mutsvangwa told reporters on Tuesday that she was not aware of the blackout. (Writing by John Stonestreet; editing by MacDonald Dzirutwe)