Jan 7, 12:19 AM EST

by Coco Jiang and Biodun Iginla, BBC News and Reuters, Seoul, South Korea
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SEOUL, South Korea -- The latest on North Korea's announcement that it conducted a hydrogen bomb test Wednesday (all times local):
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3:15 p.m.
U.S. intelligence-gathering aircraft have been taking off from an American air base in southern Japan, a day after North Korea said it tested a hydrogen bomb.
At least three planes departed Thursday from Kadena Air Base on the Japanese island of Okinawa.
It wasn't clear what they were doing, but they could be involved in trying to determine what kind of nuclear device North Korea detonated.
One of the aircraft seen departing, the RC-135S, collects optical and electronic data from ballistic targets. It is used for arms treaty compliance verification and U.S. strategic and missile defense development.
White House spokesman Josh Earnest told reporters in Washington on Wednesday that "the United States will be collecting additional evidence" and working closely with other countries in the region to learn more about the North Korean test.
- Koji Ueda, Okinawa, Japan
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11 a.m.
South Korea is limiting entry to an industrial park in North Korea jointly run by two Koreas in its first concrete action since Pyongyang said it had carried out a successful hydrogen bomb test.
The Unification Ministry says visitors who are not directly related to business operations in Kaesong industrial park will be denied entry. It affects clients, potential buyers and service providers to 120 South Korean businesses in the North Korean border city.
South Korean companies - mostly small- and medium-sized - make products such as watches and fashion goods with cheap labor from North Korea. The park, which employs about 53,000 North Koreans, is the last major inter-Korean project from the era of rapprochement