South Sudanese President Salva Kiir on Thursday suspended his First Vice President Riek Machar, just hours after the justice ministry filed charges of treason, murder and crimes against humanity against him. The decision was announced in a presidential decree broadcast on state radio.

Justice Minister Joseph Geng told reporters that Machar faces accusations of orchestrating ethnic militia attacks against federal forces in Upper Nile State in March.

According to Geng, Machar and seven others – including former oil minister Bot Kang Chol – are alleged to have directed operations by the “White Army” militia, which resulted in heavy casualties and serious human rights violations.

The case marks the most serious escalation yet in the long-running power struggle between Kiir and Machar, who has been under house arrest since March.