The North has ignored sanctions, warnings and appeals to come to the negotiating table.
The workers report losing a fifth of their monthly wages with the new currency.
The isolated country routinely employs the tactic whenever sanctions are imposed.
Working in collusion with police, they demand money for permission to load trucks and transport goods.
The order to 'stand by' is delivered to factories and firms in one province by military helicopters, sources say.
They are fishing for squid to sell abroad and in domestic markets for Chinese renminbi and US dollars.
Foreign ministers of Philippines and North Korea also meet on sidelines of ASEAN Regional Forum.
At meeting in Manila, Southeast Asia’s top diplomats express “grave concerns” about escalating tensions on Korean Peninsula.
Some fail to return to their posts as newer staff are sent out, leaving a number of positions unfilled.
American embassy asks ASEAN Regional Forum members to use meeting to highlight Pyongyang’s “unacceptable” behavior.
They must watch what they say when traveling in China, North Korean officials tell them.
North Korea in coming days will take part in a regional meeting hosted by Manila.