Chad has arrested a group of people for conspiring in what the government described as a "destabilisation plot" in the landlocked central African country, which has a history of instability.
The government serving under President Idris Deby Itno, who himself came to power in a 1990 coup, said a "small group" was involved while police and opposition sources said one of the detainees was an opposition lawmaker.
The situation appeared calm in the Chadian capital on Thursday, with residents going about their usual day-to-day activities normally.
A police source said soldiers and civilians also took part in the alleged plot.
"A small group of ill-intentioned individuals attempted to carry out a destabilisation plot against the institutions of the republic," the government said in a statement Wednesday.
The government said the army had "neutralised" the group and that the arrested ringleaders had been handed over to prosecutors for investigation.
"This small group... had been conspiring for more than four months to jeopardise the country's hard-won peace," it said.
Between 2005 and 2010, the former French colony was wracked by civil war.
On Saturday, Deby told Radio France Internationale that "mercenaries", currently in Libya's second largest city Benghazi, were trying to "regroup Chadians".
A police source said that "several civilians and soldiers, including Saleh Makki," an opposition lawmaker, had been arrested Monday.
Opposition leader Saleh Kebzabo said in an email to AFP that he received reports of "numerous" arrests in the capital N'Djamena and that "several sources" had confirmed to him that Makki was among those arrested.
France on Thursday said it had noted the latest events in Chad "with concern", and called on the country's government and opposition to engage in "calm and constructive dialogue" with each other.
Chad, once known as one of the world's poorest nations, has had a history of instability.
In March 2006, the government said soldiers and police had thwarted a bid to overthrow Deby's regime and kill him by shooting down his aircraft.
The regime has also faced rebellions in the last few years, especially in the east of the country, which borders the Sudanese region of Darfur.
In 2008 rebels from the border region came close to overthrowing the Deby regime, briefly entering the capital before being pushed back with the help of French forces.
Deby himself first came to power in a coup in December 1990 when he overthrew Hissen Habre, who seized power in 1982 after a two-year civil war. Deby had been Habre's military adviser.
Six years later he won the sub-Saharan nation's first multi-party presidential election since independence from France in 1960.
Earlier this year, Chad sent around 2,000 troops to Mali to contribute to a French-led military offensive to dislodge Islamist extremists who had seized large swathes of the north last year.
Its parliament voted this month to gradually withdraw the troops, which are highly trained, well equipped and experienced in desert warfare.
Analysts saw Deby's deployment of the largest African force to Mali as a bid to carve out a role as a force for regional stability.
But ousted Central African Republic (CAR) leader Francois Bozize accused his former Chadian allies in neighbouring Chad of militarily backing the rebels who unseated him in March.
Chad, which had months ago ordered troops into the CAR to act as a buffer against the rebels, denies the charge.
Congolese officials said Chad's foreign minister would attend a meeting Thursday in Brazzaville to discuss the crisis in the Central African Republic.