By deploying troops and sealing borders to try to quell ethnic clashes in eastern Chad, President Idriss Deby risks worsening tensions and economic fallout in a region that is already trigger-sensitive, analysts say.

Deby on Monday announced the deployment of 5,000 troops and declared a state of emergency in the provinces of Sila and Ouaddai, where dozens of people have been killed.

Tensions between indigenous settled farmers and nomadic Arab herders, often over access to grazing land and trampled crops, have simmered for years, sometimes erupting into clashes.

Visiting Sila, where an eruption of violence had claimed more than 50 lives earlier this month, Deby called for the disarming of all civilians and authorized the military to fire on troublemakers.

"If fighting persists between Arabs and (local) Ouaddaians you shoot 10 from each side to save the majority," he advised.

Lawmakers from the ruling party have welcomed the government's campaign to halt the violence.

But rights activists and even some in the armed forces worry the mission may fail, lead to abuses or inflict economic damage that will further antagonise the rival communities.

The three-month state of emergency is accompanied by a provincial curfew, a ban on riding motorbikes -- which are often used for hit-and-run attacks -- and a closure of Chad's borders with Sudan and Libya.

A state of emergency was also clamped on the northeastern province of Tibesti on Libya's southern border. The arid mountainous terrain has long provided hideouts for Chadian rebels and attracts illegal gold diggers.

"The government's decision has come at the right time," said Ouchar Tourgoudi, a member of parliament for Ouaddai, from the ruling party.

"These measures are what we asked of the central government to eradicate these conflicts."

Others said his regime should have acted earlier.

"It's a good thing the state has finally reacted, even if it's late," said the founder of the Citizen's Movement for the Preservation of Liberties in Chad, Jean-Bosco Manga.

"The upsurge in violence has reached a worrying level because of the state's weakness and lack of diligence."

In a statement, the Chad Convention for Human Rights expressed outrage at "the call to massacre civilians."

"Responsibility for the genocide that is being prepared will lie with President Deby," it said.

N'Djamena officials argue that closing borders with two nations ravaged by armed struggle will limit the circulation of weapons in the troubled territory, but rights activists fear the fallout.

The measure "could have terrible effects on the local economy for these populations that already survive with difficulty," Manga said.

For the leader of the Union of Democrats for Development and Progress, Max Kemkoye, the two eastern provinces "obtain supplies largely from Sudan, including basic products like food and medicines."

"The state of emergency will give unlimited power to the security forces, whose abuses of authority and human rights violations have potential to complicate the situation," said Ahmat Yacoub Dabio, president of the Study Centre for the Prevention of Extremism in Chad.

He called for "the dissuasive reinforcement of police forces in all villages at great risk" and "a conflict prevention strategy" based on dialogue.

A senior army officer serving in Ouaddai province agreed, asking not to be named.

"The region is vast and we are not immune from possible trouble. The government determines a state of emergency and we carry out orders, but will that resolve the conflict between farmers and herders?"

"Security measures can change things, but they must be complemented by other steps," said Kelma Manatouma, a Chad specialist at the University of Paris at Nanterre.

The global climate crisis has become the key to the communal conflict in Chad, according to Manatouma. Grazing areas available to nomadic herders have shifted, while the land available for cultivation by farmers has shrunk, he said.

"Economic and social justice must be central," he added, noting that Ouaddaian farmers protest at the perceived impunity granted the herders, who mostly come from Deby's Zaghawa ethnic group.