Ethiopia's parliament voted unanimously on Thursday to extend the country's state of emergency for another four months after Defence Minister Siraj Fegessa told it some "anti-peace forces" were still at large.

The state of emergency, imposed last October following months of deadly protests that killed around 500 people, had generally brought back stability although some areas were still "less calm," he said without elaborating.

"Those responsible for committing such acts should all be apprehended before the state of emergency is lifted," said Siraj, who chairs a command post to oversee implementation of the decree.

The state of emergency was imposed after protests mostly in the Oromiya region around the capital Addis Ababa. Anger over a development scheme for the city had turned into broader anti-government demonstrations over politics and human rights abuses.

The government has since lifted some restrictions, ending stop and search powers for security services and dawn-to-dusk curfews on access for unauthorised people to certain economic installations, infrastructure facilities and factories.

A rule barring diplomats from traveling beyond a 40 kilometer (25 miles) radius of the capital without permission was also lifted.

But other restrictions remain. Contacts with opposition groups branded as "terrorist movements" are still forbidden. Ethiopia has designated five groups, including two armed secessionist groups, as terrorist organisations.

Another directive barring the "preparation, distribution and exhibition of material that could incite chaos" remains intact.