Police said twelve protesters were arrested in N’Djamena during small marches against President Idriss Deby, who has ruled Chad for 27 years.
The rallies, which were planned by civil society groups, trade unions and opposition politicians, were banned by the authorities in advance, who cited “security” reasons.
But civil society leader Mahamat Nour Ibedou and about 20 other people staged a small demonstration in the city centre, while a separate group of some 10 people also protested in the south of the city, chanting anti-Deby slogans.
This “day of anger is a day of joy because people have gone about their business”, police spokesman Paul Manga told AFP.
“We arrested 12 people in different parts of the city,” he said, adding they would be referred for prosecution without specifying on what charges.
On Wednesday, the government suspended 10 opposition parties for two months for “disturbing public order” and “inciting violence” after they backed the protests.
A day earlier, opposition politicians took part in another march that was dispersed by police, causing injuries, according to the opposition.
Trade unions have initiated a number of strikes in the last two weeks over the state of the economy.
A Western ally in combating jihadism in the volatile Sahara region, Chad has endured two years of severe recession worsened by a slump in oil prices.
The impoverished Sahel state is imposing cuts in public spending that the finance ministry says are vital to stave off bankruptcy.
But the cuts have increased social tension and anger towards Deby.
Almost half the population of 14 million lives below the poverty line, according to the World Bank.