WASHINGTON: The US Defense Department is "looking into reports of a possible seismic event near North Korea's nuclear facilities," a US official said on Tuesday.

South Korea's meteorological agency said earlier that North Korea is "likely" to have conducted a nuclear test that caused an earthquake near a known testing site in the isolated country.

"We are looking into the reports of a possible seismic event near North Korean nuclear facilities," said a US official, who spoke on condition of anonymity.