Sudanese civilian staff in the world's largest peacekeeping operation have staged a strike over wages, the mission said on Thursday, as the country's economy faces a sinking currency and steep inflation.

"UNAMID's national staff held yesterday a strike", the African Union-UN Mission in Darfur said, without specifying exactly how many of the roughly 2,900 local workers took part.

It said local employees received a pay increase earlier this year but "consider the increase as insufficient and demand to be either paid in US dollars or to have their salaries recalculated according to the June 2012 exchange rate."

Sudan's currency has plunged in value on the black market since Khartoum lost its largest source of hard currency in July 2011 when South Sudan separated with roughly 75 percent of the unified country's oil production before independence.

Trying to address the fiscal imbalance, Khartoum in June announced a series of measures including a devaluation of the pound from 2.70 per dollar to a range up to 5.30 pounds per dollar.

The new rate is nearer the black market price of roughly six pounds.

Sources familiar with the situation said UNAMID is still paying its staff in Sudanese pounds at the old exchange rate of around 2.70.

"They don't necessarily want to get dollars. They want to get paid at a fair rate," one source said, adding that the raise offered for most local staff earlier in the year was about four percent.

Declining to be identified, the sources said the strike occurred only after months of unsuccessful talks with UN headquarters in New York. If there is no resolution, job action will escalate to two days next week and a full week thereafter, they said.

"I understand your concerns and I am committed to work hard with the UN headquarters to look into these issues," acting UNAMID head Aichatou Mindaoudou told the local staff in a meeting on Wednesday, the mission said in a statement.

Sudan's inflation was 41.6 percent in July compared with a year earlier, official data showed, continuing a painful price spiral that prompted demonstrations around the country in June and July.

UNAMID has been in Sudan's far-western Darfur region for more than four years with a mandate to protect civilians in the vast area where rebel-government clashes, banditry and inter-tribal fighting continues, though violence is less than when rebels began an insurrection nearly a decade ago.

With more than 22,000 international troops and police officers, UNAMID has a budget of about $1.4 billion for 2012-13.