The South had halted operations at the industrial park in reaction to Pyongyang's missile launch.
U.S. officials say that the satellite, which caused an international outcry, is incapable of any useful function.
Tens of thousands of tourists have also been stranded, as snow grounds flights.
Authorities have made three arrests since the militant group's first-ever attack on Indonesia.
The unidentified aerial vehicle crossed into South Korean territory on Wednesday.
The United Nations Secretary General was speaking ahead of an emergency meeting of the U.N. Security Council.
South Korea launched a live-fire drill around Yellow Sea islands to mark the five-year anniversary of shelling by the North.