Addis Ababa - Ethiopia's Prime Minister Hailemariam Desalegn declared a six-month nationwide state of emergency on Sunday, saying months of unrest threatened the nation's stability.
Rights groups say more than 500 people have been killed in protests in the Oromiya region since last year, when anger over a development scheme for the capital turned into broader anti-government demonstrations over politics and human rights abuses.
The government says the death toll is inflated.
"A state of emergency has been declared because the situation posed a threat against the people of the country," Hailemariam said on state-run television.
"Vital infrastructure, businesses, health and education centres, as well as government offices, and courts have been destroyed," he said.
He also repeated earlier promises of reform and plans for dialogue with the opposition.
The state of emergency was effective from October 8.
The violence in Oromiya, Ethiopia's largest and most populous region which surrounds the capital Addis Ababa, and to a lesser extent in the Amhara province, has cast a shadow over a nation where a state-led industrial drive has created one of Africa's fastest growing economies.
But the government also faces rising international criticism and popular opposition to its authoritarian approach to development.
The unrest has included attacks on businesses, many of them foreign-owned, including farms growing flowers for export.
Attorney General Getachew Ambaye said the decree would permit authorities to stop and search and also detain suspects without court authorisation, as well as carry out house searches.
It also bars the "preparation, distribution and exhibition of material that could incite chaos", he said in an official announcement.
The measures did not contain curfews, but Getachew said the command post set up to oversee the implementation of the legislation and chaired by Hailemariam would determine where and when to impose curfews "should the need arise".
"Failure to observe the measures would lead to imprisonment for a period of five years," he said.
Mulatu Gemechu, deputy chairperson of the opposition Oromo Federalist Congress, told Reuters that the unrest could worsen if security forces were to be granted more powers and expand their presence in Oromiya.
"These are peaceful protesters who have been demanding that soldiers are pulled out. This could intensify anger," he said.
Last Sunday, scores of people were killed in a stampede triggered when police used teargas and shot in the air to disperse anti-government protesters at a religious festival in the town of Bishoftu.
A US researcher was killed on Tuesday when her car was attacked by stone-throwers near Addis Ababa.
Reuters