The United States flew surveillance aircraft over the Korean Peninsula on Monday, an aviation tracker said, amid simmering tensions over possible provocative acts by North Korea after it warned of a "new strategic weapon."

An RC-135W Rivet Joint of the US Air Force carried out operations over South Korea at 31,000 feet, Aircraft Spots tweeted.

It added the flight took place Monday.   

This type of aircraft was last spotted over the peninsula on Wednesday, according to the aviation tracker. Several other surveillance aircraft, such as the EP-3E and the RC-135S, have conducted operations here often in recent weeks.

The latest flight came amid growing concerns over its provocative acts ahead of the birthday of its leader Kim Jong-un that falls on Wednesday.

Wrapping up a rare four-day party plenum last week, Pyongyang said it no longer feels bound by the self-imposed moratorium on nuclear and long-range missile tests, and warned that the world would witness a new strategic weapon "in the near future" amid stalled denuclearization talks with the US.

Experts say the North's "strategic weapon" may mean an intercontinental ballistic missile capable of carrying multiple warheads or a submarine-launched ballistic missile. (Yonhap)