State security minister Owen Ncube announced the arrests on television and thanked security forces for "standing firm" in the face of the country's most serious unrest since deadly post-election violence in August.
While some hungry Harare residents reported being tear-gassed by police when they ventured out for bread, President Emmerson Mnangagwa denounced what he called "wanton violence and cynical destruction." He noted a right to protest and said he understands the "pain and frustration," but he appeared to side with authorities who blame the opposition for unrest.
Pastor Evan Mawarire was clutching a Bible when police bundled him into their car in the capital. He famously organized what became nationwide anti-government protests in 2016 against mismanagement and then-President Robert Mugabe's long stay in power.
"They are alleging that he incited violence through Twitter and other forms of social media," said Beatrice Mtetwa, the pastor's lawyer.
There were widespread reports of violence as Zimbabwe faced a third day of protests over what has become the world's most expensive gasoline.
The country's largest telecom company, Econet, told customers the government forced it to shut down internet service. "The matter is beyond our control," it said. Service returned hours later but social media was blocked.
In a grim recounting of alleged police violence, the Zimbabwe Association of Doctors for Human Rights said late Wednesday it had treated 68 cases of gunshot wounds and 100-plus other cases of "assaults with sharp objects, booted feet, baton sticks" and more. It noted bites from the alleged unleashing of police dogs, and the "dragging of patients with life-threatening conditions" to court.
Armed police and soldiers broke up groups of more than five people in Harare, while desperation for food forced some people to venture into the streets. But virtually all shops were closed.
Police fired tear gas after a crowd tried to overrun a shopping center that opened to sell bread. Soldiers with AK-47s took charge of the long line.
"This kind of life is unbearable, we have soldiers at fuel queues and now soldiers again are controlling the bread queue," one man said. "Are we at war?" He spoke on condition of anonymity out of concern about possible retaliation.
A spokesman for the main opposition MDC party, Nkululeko Sibanda, said in a Twitter post that "party leadership" had been detained. "This is only deepening the political crisis," he said.
As Mnangagwa makes an extended overseas trip that will include a stop at the World Economic Forum in Davos, Switzerland, to plead for more foreign investment, former military commander and Vice President Constantino Chiwenga, a hardliner, is in charge at home.
Reported death tolls this week have varied. Eight people were killed on Monday when police and military fired on crowds, Amnesty International said. Zimbabwe's government said three people were killed, including a policeman stoned to death by an angry crowd.
The demonstrations amount to "terrorism," Information Minister Monica Mutsvangwa has said, blaming the opposition.
International concern has been rising over Zimbabwe in recent months after a burst of optimism when Mugabe stepped down in late 2017 under military pressure.
"We hope that people are able to demonstrate peacefully and freely," said United Nations spokesman Stephane Dujarric.
The British minister for Africa, Harriett Baldwin, has noted "worrying levels of violence" and urged restraint by security forces. But South Africa's foreign ministry said in a statement that "we're confident measures being taken by the Zimbabwean government will resolve the situation."
Zimbabweans in neighboring South Africa protested outside their embassy. Tino Mambeu called the arrest of Mawarire, the pastor, "madness, thus absolute rubbish."
Associated Press video journalist Nqobile Ntshangase in Pretoria, South Africa and writer Edith M. Lederer at the United Nations contributed.
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