SEOUL -?Labourers of the Democratic People's Republic of Korea(DPRK) did not report to work early on Tuesday at the Kaesong industrial zone it jointly operates with?the Republic of Korea(ROK), Yonhap news agency reported, a day after Pyongyang said it would withdraw workers and suspend operations indefinitely.

Isolated and impoverished?DPRK suspended work at Kaesong, its sole remaining major project with the ROK, on Monday amid what has become one of the most serious crises on the Korean peninsula since the end of the Korean War in 1953.

It is the first stoppage since the Kaesong industrial project began shipments in 2004.

Tensions have been rising since the United Nations imposed new sanctions against the?DPRK after Pyongyang carried out its third nuclear test in February.

Speculation has increased it will carry out some sort of provocative action -- either another nuclear test or a missile launch -- deeply worrying?ROK and its major ally the United States.

A?ROK's government official could not immediately confirm the Yonhap report on Tuesday and said authorities were investigating.

The Kaesong complex employs more than 50,000?DPRK workers?and is one of the DPRK's few sources of ready cash.

On Monday, the DPRK's official news agency KCNA cited senior official Kim Yang-gon as saying?DPRK would decide later whether it would continue to operate the zone.

About 475 ROK?workers remain in Kaesong a week after?DPRK banned all the Republic of Koreans?from entering the complex. The South's Unification Ministry said 77?ROK workers were expected to return home on Tuesday.

Thirteen factories have stopped operations in Kaesong due to lack of raw materials, according to the Unification Ministry. A total of 123?ROK companies generate more than $80 million a year in cash in wages at the complex.

An executive at a?ROK apparel firm running a factory in Kaesong said late on Monday his employees had told him they would stay on at the factory.

"I don't know what to do, honestly. I can't simply tell my workers to leave or stay," said the executive, who requested anonymity.