New Delhi, July 8 -- A government-appointed county commissioner in an opposition stronghold in South Sudan's oil-rich Jonglei State was "assassinated" by opposition forces in renewed violence, the government confirmed late Monday.

Fighting in Jonglei has intensified in recent days, with an unknown number of casualties. The strategic county of Akobo has seen the appointment of both government-backed and opposition-backed county commissioners.

James Kueth Makuach, the government-appointed commissioner, was killed on Sunday when opposition fighters launched an assault on Walgak, a remote area in Akobo West, according to officials from both sides.

Makuach defected to President Salva Kiir's ruling party in April after being removed by the o...