The United States again flew a surveillance aircraft over the Korean Peninsula, an aviation tracker said Thursday, 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 without specifying the exact time of the operation.

This type of aircraft has been spotted conducting missions above the peninsula over the past several days in a row, along with several other surveillance aircraft such as EP-3E and RC-135S aircraft, according to the aviation tracker.

The flight came after North Korean leader Kim Jong-un said Pyongyang no longer feels bound by the self-imposed moratorium on nuclear and long-range missile tests and that the world would witness a new strategic weapon "in the near future," according to the North's Korean Central News Agency on Wednesday.

The communist country has not conducted such tests since November 2017 when Kim announced a halt to all its nuclear and intercontinental ballistic missile tests, which Trump has touted as one of his key diplomatic achievements.

As its denuclearization negotiations with Washington have made little progress, however, Pyongyang has warned of taking a new way other than dialogue, and Kim said his country "will shift to a shocking actual action."

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