The UN Security Council has confirmed that a UN cargo helicopter that crashed in South Sudan had been attacked and called for those responsible to face justice.

The Mi-8AMT helicopter from the UN mission in South Sudan (UNMISS) went down yesterday, near the northern oil town of Bentiu, killing three Russian crew members and injuring a fourth.

The council said in a unanimous statement put forward by Russia that it condemned the downing.

It said that "this attack constituted a grave violation that jeopardized UNMISS operations."

The 15-member council urged UNMISS and the South Sudan government to conduct a "swift, thorough and transparent investigation" and said "those responsible must be held accountable."

South Sudan army spokesman Philip Aguer earlier said rebels "shot it down," but provided no evidence.

Rebel spokesman Mabior Garang dismissed the claim as "malicious allegations."

"The area in which the plane (helicopter) was reportedly shot down is government-held territory, if indeed the aircraft was shot down," Mr Garang said.

Bentiu has been badly damaged in heavy fighting between government and rebel forces that was sparked by a power struggle between President Salva Kiir and his sacked vice president Riek Machar.

A UN team was investigating the wreckage of the helicopter today.