Hwang Jin-ha, a lawmaker from South Korea's ruling Grand National Party, said the country's top intelligence chief warned of a likely nuclear test in the future, South Korea's Yonhap news agency reports.
"A nuclear test is possible at any time as (North Korea) has various nuclear test sites and some construction is under way," the lawmaker was quoted as saying.
Without providing a time frame, the lawmaker said intelligence officials felt there was a "slim" chance that a nuclear test was imminent.
North Korea left international nuclear talks in 2009 and Seoul said it considered a military response from Pyongyang was likely if the regime was backed into a corner.
The nuclear warning followed an executive order from U.S. President Barack Obama that reinforced an arms embargo on North Korea.
The U.S. Geological Survey detected seismic indications in 2006 that in part verified North Korean claims that it tested its first nuclear device. Two similar reports surfaced in 2009.