NAIROBI, Kenya (AP) — Somalia's government has ordered the United Nations envoy to the country to leave, amid questions over the arrest of the al-Shabab extremist group's former deputy leader who had run for a regional presidency.

A foreign ministry statement late Tuesday accuses Nicholas Haysom of diplomatic overreach that violated the Horn of Africa nation's sovereignty, declaring him "persona non grata."

Haysom had questioned the legal basis used in the arrest last month of Mukhtar Robow and whether U.N.-funded regional police in the Southwest were involved.

Ethiopian troops who are part of the African Union force in Somalia and Somali police arrested Robow days before the regional election. Deadly protests followed.

Robow was flown to Mogadishu and has been held in a prison run by Somalia's intelligence agency.

The U.N. has not commented.