Seoul and its allies are on heightened alert with signs linked to missile launch preparations being detected in North Korea, local and foreign government officials said Tuesday.

“Signs that match those leading up to a missile launch have been detected in North Korea, and surveillance of North Korea has been stepped up,” an unnamed government official was quoted as saying by the local media.

Local news outlets also reported that North Korea operated radar equipment used to track missile trajectories on Monday, while communications within their missile base showed an unusual spike. 

The US, for its part, has said that North Korea’s activities are being closely monitored.

“We watch North Korea very closely. We‘ll continue to do so,” Army Col. Robert Manning, a Pentagon spokesman, told reporters.

“The Republic of Korea (South Korea) and US alliance remains strong, and capable of countering any North Korean provocations or attacks.”

Manning also said that Washington continues to seek a diplomatic means to dismantling North Korea’s nuclear weapons program.

“The State Department is working very hard to exercise those diplomatic options and initiatives and efforts with China,” Manning said when asked if China, North Korea’s main ally and economic benefactor, can still be trusted.

South Korea’s military also said Tuesday that it is keeping a close eye on North Korea.

“Our armed forces are closely following and monitoring (North Korean activities) in cooperation with the US, leaving open all possibilities,” JCS spokesman Army Col. Roh Jae-cheon said Tuesday, declining to comment about Japanese media reports.

Earlier in the day, Tokyo-based news agency Kyodo News reported that the Japanese government has detected communications signals indicative of a possible missile launch, citing a number of government officials.

The report quoted Japanese government officials as saying that a launch could be possible within days, and added that the type of missile North Korea may fire is unclear.

The report, however, added that as movement of missiles or mobile launchers have not been detected, the Japanese government has not ruled out the possibility that the signals may have resulted from military exercises.

The reports come amid growing speculation over North Korea’s plans.

North Korea has remained quiet for more than two months, despite its threats against the US and warning of retaliation following US President Donald Trump’s address to the UN General Assembly in September. North Korea’s most recent provocation came in the form of an intermediate range ballistic missile launch on Sept. 15.

In his address, Trump said that Pyongyang was on a suicide mission, and that an attack against the US or her allies would result in total destruction of North Korea.

In response, North Korea warned of retaliation of the “highest measure,” which according to Pyongyang’s Foreign Minister Ri Yong-ho could take the form of a hydrogen bomb test in the Pacific.

While Pyongyang remains quiet, a recent news report citing a Chinese official claimed that the regime’s nuclear weapons program is nearing completion, and that a nuclear weapons test -- the most powerful yet -- could be conducted in the near future.

By Choi He-suk (cheesuk@heraldcorp.com)