At least 30 people were killed in Bor, the capital of the oil-rich Jonglei state in South Sudan, during clashes between local young demonstrators and peacekeepers from the UN Mission in South Sudan (UNMISS), the Paris-based Sudan Tribune website reported on Friday.

The clashes erupted on Thursday when armed youths from Bor town opened fire at the UN compound where thousands of internationally displaced people (IDPs) in the country are currently sheltering.

UNMISS health worker William Oyual said 20 people were killed when armed local youths forced their way into the compound.

Bior Kuer, who works at Bor civil hospital, said another two people died at the health facility from wounds suffered during the fighting.

According to Kuer, 14 others were wounded, with three in critical condition.

UNMISS confirmed the fighting through spokesman Joe Conteras in Juba, but has yet to provide further details.

The UN base housing an Indian contingent of peacekeepers was overrun by the youths, who opened fire indiscriminately, killing people including women and children.

It is not yet clear what provoked the attack. The South Sudan army's (SPLA) director of information and public relations Brig. Gen Maluak Ayuen said the incident in Bor occurred after civil society representatives delivered a memo against Machar supporters in the UNMISS compound.

Meanwhile, Machar's spokesperson James Gatdet Dak condemned the killing of IDPs "in the strongest terms possible."

"Many survivors confirmed to me that many people were killed and the base was deserted. Some of the survivors had to run to the wild, while others made it to the other official camps of the Korean contingents," he said.

South Sudan has been witnessing bloody clashes between government troops and forces loyal to former vice-president Riek Machar since mid-September last year.