The cost of a dollar on the parallel market rose to 11.05 Sudanese pounds on Wednesday from 10.5 pounds per dollar at the start of the week, traders said. The government has kept the official rate at 6.4 pounds to the dollar since August.
"It is now difficult to find large amounts of dollars in the black market. There is not enough dollars in the market," a parallel market trader said.
Sudan's annual inflation rate eased to 13.37 percent in October from a revised 13.56 percent in September, a monthly report from Sudan's Central Statistics Office said last month.
"As of today our company has stopped making sales. We're not able to transfer hard currency to the company we act as an agent for in Sudan," said a businessman who imports medical equipment.
"What's happening now has hit our company and other companies that import items. Sudan's economy is really in a big crisis," he said.
Prices soared in Sudan after South Sudan seceded in 2011, taking with it three-quarters of the country's oil output, the main source of foreign currency used to support the Sudanese pound and to pay for food and other imports.
Fuel subsidy cuts introduced in 2013 also pushed up inflation, but their effects have since begun to ease.