South Korea voiced regret Thursday at North Korea's decision to spurn an offer of formal talks on removing goods from a joint industrial complex closed by military tensions.

"It's very regrettable," said Unification Ministry spokesman Kim Hyung-Suk, again urging Pyongyang to negotiate over the South Korean firms forced to withdraw from the Kaesong zone, 10 kilometres (six miles) inside North Korea.

At the request of President Park Geun-Hye, the Unification Ministry formally proposed talks at the truce village of Panmunjom in the Demilitarised Zone which bisects the Korean peninsula.

But the North reacted negatively on Wednesday, calling the offer "a crafty ploy" to deflect blame for the suspension of operations at Kaesong.

Established in 2004 as a rare symbol of inter-Korean cooperation, the joint industrial zone was the most high-profile casualty of two months of elevated tensions that followed the North's nuclear test in February.

The North barred South Korean access to the zone and pulled out its own 53,000 workers early last month. Seoul withdrew the last of its nationals 10 days ago.

When they left, officials from the firms loaded up cars with bundles of products, but were still forced to leave large stocks of goods behind.

Neither side has officially declared a permanent shutdown of Kaesong, with the South continuing to supply a minimum amount of electricity to the empty complex.

Pyongyang has said restarting the complex would require Seoul to cease all "hostile acts and military provocations" including joint military drills with Washington.

The last group of South Koreans left Kaesong on May 3 after the South sent $13 million in cash to the North to cover unpaid wages and taxes.

On Wednesday, President Park said the North had a responsibility to return company property once all the outstanding dues had been paid.

"If North Korea holds on to the finished products and raw materials ... it will push itself into a corner," Park said, urging Pyongyang to do the "gentlemanly" thing.