N.Korea a 'serious threat' to US: Panetta

North Korea is a "serious threat" to the United States and Washington must be prepared to deal with it, US Defense Secretary Leon Panetta warned Tuesday after Pyongyang conducted a nuclear test.

"We saw what North Korea has done these last few weeks with a missile test and now a nuclear test," the outgoing defense secretary said at a military farewell ceremony.

"North Korea represents a serious threat to the US. We've got to be prepared to deal with that."

Panetta's comments came after North Korea announced it had tested a "miniaturized" device in its third nuclear test. US intelligence confirmed that North Korea probably conducted an underground nuclear explosion with a yield of several kilotons.