A boycott by North Korean workers halted operations at the joint-Korean Kaesong industrial complex on Tuesday, the latest blow from Pyongyang to its only symbol of economic cooperation with South Korea.

Around 53,000 North Korean workers did not show up for work after Pyongyang shuttered Kaesong to “examine the issue” of whether it will allow its existence or close it.

Kim Yang-gon, secretary of the North Korean Communist party’s central committee, said South Korea and US “insults” to his “country’s dignity” led to the closure of Kaesong.

“How the situation will develop in the days ahead will entirely depend on the attitude of the South Korean authorities,” Kim said.

South Korea said it will “calmly but firmly handle North Korea’s indiscreet action,” reports the Financial Times.

The decision “cannot be justified in any way and North Korea will be held responsible for all the consequences,” the unification ministry in Seoul said.

The move deals a blow to South Korean companies operating in the complex on the northern side of the border, which are estimated to have invested $500 million so far.

But the North Korean regime will suffer losses of millions of revenues it makes from the business park, analysts said.