South Sudan has handed over to Ethiopia 15 people suspected to have been involved in last month's killings in the Gambella region, west of the capital, Addis Ababa.

MAP OF ETHIOPIA

Official reports from Gambella say the 15 suspects were arrested in Jonglei in South Sudan before being handed over to Ethiopian authorities.

One suspect, according to authorities, is still at large.

The two Horn of Africa countries recently signed an extradition agreement, sparking hue and cry among critics that the agreement could be a ploy to silence Ethiopian opposition groups.

Two months ago, unidentified gunmen killed 20 students in an attack on a bus as they travelled to Gambella.

The latest incidents have sent a wave of fear among private agricultural investors in the fertile Gambella region.

Gambella region, which borders Sudan, has attracted many foreign commercial rice farmers.

But international and human rights organisations and local opposition parties have criticised the Ethiopian government's land policy as being tantamount to "land grabs", arguing that local people will not benefit from the move.