Ethiopian police have arrested two senior opposition members on suspicion of inciting weeks of protests against government plans to set up a new economic zone near the capital that would displace farmers, their party leader said on Friday.

The Oromo Federalist Congress (OFC) says 87 protesters have been killed by police since demonstrations broke out this month in Oromiya region, in the country’s worst civil unrest for a decade.

On Dec. 15, a government spokesman said police had a list of five people who had died during the protests, but casualties could be higher. Officials have yet to announce an updated number.

OFC chairman Merara Gudina said police rounded up his deputy Bekele Gerba and the party’s assistant secretary Dejene Tafa on Thursday, and both remained in custody.

“They suspect that our party and some of our members are part of the protest movement, that we have been inciting the demonstrations,” he told Reuters, denying that the OFC had incited violence. “We do not know when Bekele and Dejene will be released or be charged for anything.”

Government officials were not immediately available for comment, but Prime Minister Hailemariam Desalegn told parliament on Friday that “anti-peace forces” had incited violence by spreading false information about the so-called “Addis Ababa Integrated Development Master Plan” to create an investment and industrial zone near the capital.

He said members of “terrorist groups” had infiltrated protesters and that the government would take “unflinching measures” against them.

Addis Ababa has accused the secessionist Oromo Liberation Front (OLF) and opposition group Ginbot 7 of involvement in the protests. It labels both groups as terrorist organizations.

Oromiya is Ethiopia’s largest region by size and population. Dissident groups such as the OLF, which is waging a low-key rebellion, accuse the ruling EPRDF coalition of marginalizing ethnic Oromos.

The second most populous nation in Africa with 90 million people, Ethiopia has long been one of the poorest countries in the world per capita, but has made startling strides toward industrialization, recording some of the continent’s strongest economic growth rates for a decade.

But reallocating land for new uses is a thorny issue in a country where the vast majority of the population still survives on smallholder farm plots. The opposition says farmers have often been forced off land and poorly compensated.