A file photo of US F-117A Nighthawk stealth fighter jet. The United States is deploying a squadron of stealth fighters to South Korea, amid speculation that North Korea may be ready to test a second nuclear device. [Reuters]

SEOUL - The United States is deploying a squadron of stealth fighters to South Korea, a US military spokesman said on Wednesday, amid speculation that North Korea may be ready to test a second nuclear device.

The United States is sending about 15 to 20 of its F-117A Nighthawk fighters to South Korea, the spokesman for US Forces Korea said.

"This is a routine deployment," said Kim Yong-kyu. "It is a regular operational matter.

The US military has sent the radar-evading fighters regularly to South Korea for stays of a few months over the past few years. North Korea has criticized previous deployments as preparations for invasion and nuclear war.

Holloman Air Force Base in New Mexico, where the squadron is stationed, said in a Web posting that the fighters left earlier this week for South Korea.

About 250 to 300 airmen were sent to South Korea for previous deployments.

"This precision-strike aircraft penetrates high-threat airspace and uses laser-guided weapons against critical targets," the US Air Force said in a Web posting.

North Korea conducted its first test of a nuclear device on October 9.

The US television network ABC cited US officials last week as saying North Korea was preparing for another test. However, both US and South Korean officials have publicly said that there was no evidence a test was imminent.