Big blast reported in North Korea
A big explosion rocked a northern province of North Korea near the border with China last week, South Korea's Yonhap new agency is reporting.
The blast on Thursday was seen from a satellite, Yonhap quoted an unnamed source in Beijing as saying.
The cause has yet to be determined, the source said.
In April, an explosion at a railway station in North Korea killed more than 150 people - but Pyongyang only admitted the incident three days later.
Yonhap quoted a diplomatic source in Seoul as saying a mushroom cloud, with a radius of 3.5-4 kms (2.2-2.5 miles), was spotted in Kimhyungjik county in Yanggang province.
But Seoul's top negotiator with North Korea, Unification Minister Chung Dong-young, reportedly played down the possibility that it might have been a nuclear weapons' test.
He said South Korea was trying to get confirmation of the explosion and its effects, Yonhap reported.
The blast is said to have happened on 9 September, as North Korea marked the 56th anniversary of its founding.