Several opposition activists and politicians were detained on Thursday in the Chadian capital NDjamena, after the government banned a rally following a failed bid to hold a vote of no confidence.
The arrests came during an attempt by the opposition to defy a ban by President Idriss Deby's government on a demonstration organised as public anger soared over the nation's growing economic crisis.
"Some 30 people were arrested," opposition chief Saleh Kebzabo told AFP. Among those held was Mahamat Bechir Barh, an opposition party leader, Kebzabo said.
The arrests were made when the demonstrators tried to march towards a stadium after holding a public meeting at the headquarters of Kebzabo's party, the UNDR.
The stadium was cordoned off by the security forces, who stopped the protesters from entering.
"Fifteen minutes later, the security forces attacked us with tear gas on the street. After that the crowds were dispersed," Kebzabo said.
The security forces then "attacked the UNDR's headquarters with tear gas", he added.
The Chadian government faced a vote of no confidence in parliament on Thursday morning. However, the vote was not held because parliament failed to make a quorum, an AFP journalist said.
The motion to bring the government down failed because the ruling party's MPs did not show, following orders from Deby.
"Of a total of 184 MPs, 110 were absent," said Kebzabo, who is also a parliamentarian.
Political, economic crisis
Opposition MPs had been seeking to hold the government of Prime Minister Albert Pahimi Padacke to account over its alleged mismanagement of the nation's economy.
Like its neighbour, oil giant Nigeria, Chad is undergoing a severe financial crisis as a result of the slump in the price of petrol.
The no confidence vote had been due to be held as a secret ballot.
The government announced a string of measures aimed at saving the economy in September.
The opposition is also critical of the political situation under Deby's iron-fisted rule.
A key ally of France in the regional fight against jihadists, Deby was swept back into power in April with 60 percent of votes. Kebzabo, his main rival, won just over 12 percent.