South Korea's defense authorities say North Korea could launch an intercontinental ballistic missile, or conduct a nuclear test, before or after next month's US presidential election.

Defense Intelligence Agency officials on Wednesday briefed a parliamentary committee on the latest developments in North Korea.

Lawmakers who attended the briefing said the officials confirmed that a mobile launcher for an ICBM has been deployed in a specific area, but no missile has been mounted yet.

The officials suggested the North could launch an ICBM to verify its atmospheric reentry technology, at a timing targeting the US presidential election in November.

The officials also said preparations inside the Punggye-ri nuclear test site in the northeast of the country are almost complete.

They have not ruled out North Korea going ahead with its seventh nuclear test around the time of the US presidential election, with the decision up to leader Kim Jong Un.

Referring to North Korean troops sent to Russia, the officials said there is a possibility that some advance units have moved to the front lines, but there is no precise information that the deployed North Korean troops are at the front lines.