New Delhi, Sept. 10 -- In the city of Bukavu in eastern Congo, Alain Mukumiro argues in a small wooden hut with a shopkeeper who refuses to take his money.

Like many in the rebel-controlled city, Mukumiro is using older, hole-punched banknotes that have been patched up and put back into circulation because of a shortage of new and intact bills.

"All my money has serial numbers, but they refuse it," Mukumiro said, upset about his ordeal.

Mukumiro, a fridge technician, said his family faces yet another night without food, like many in Bukavu, the capital of South Kivu province.

The Rwanda-backed M23 rebel group captured the city in February following an escalation of fighting between the insurgents and Congolese forces in the country's ...