North Korea agreed to fully reopen its border crossing Tuesday to South Koreans commuting to jobs at factories in a northern economic zone, according to the Unification Ministry in Seoul.

The full reopening comes four days after Pyongyang shut down the border last week, stranding hundreds of South Koreans who work in Kaesong but live in South Korea.

North Korean officials agreed to let them return home Monday, but refused entry to others seeking to travel into Kaesong. The partial closure meant factories in the industrial zone had no new deliveries of goods for days.

The North Korean military relayed a message Tuesday saying it would reopen the border to traffic from the south, Unification Ministry spokeswoman Lee Jong-joo said in Seoul. More than 540 South Koreans were expected to cross into the north, while some 300 applied for permission to head south Tuesday afternoon, she said.

North Korea has provided no explanation for the closures, which have unnerved business owners who rely on South Korean managers, expertise and raw materials for factories that employ some 38,000 North Korean workers just across the border.

Pyongyang had criticized Seoul's decision to go ahead with 12 days of joint military exercises with the U.S. last week at a time of heightened tension on the peninsula. As the war games got under way last Monday, the North's military severed the only communications hot line between the Koreas and banned traffic across the border.

Relations between the two Koreas have deteriorated since President Lee Myung-bak took office a year ago with a new, tough policy on Pyongyang. One by one, joint projects developed during the previous era of warming ties have been suspended.

The Kaesong complex, the most prominent of the landmark inter-Korean projects and a lucrative source of hard currency for the impoverished North, has been allowed to operate with a skeleton South Korean staff.

The recent closures, however, left many factories languishing without the goods needed to produce the watches, shoes, electronics equipment and kitchenware churned out from some 100 plants in the complex, the Kaesong business association said Monday.