North Korea may soon conduct its sixth nuclear test in the face of the United States' decision to move a carrier group toward the region.

Satellite imagery shows activity at the Punggye-ri testing site, analysts from 38 North, a U.S. research institute that monitors North Korea, wrote on its website Wednesday.

Foreign journalists inside the country were told to prepare for a "big and important event" Thursday, Reuters reported.

The analysts added that there was movement around one of the portals and in the main administrative area of the site as well as personnel seen at the command center.

South Korean officials downplayed any news signs that a test was coming, Bloomberg reported. South Korea’s Joint Chiefs of Staff spokesman Roh Jae-cheon told reporters that Seoul saw no signs that North Korea was preparing any sort of provocative actions. Officials added that Pyongyang has maintained such readiness that it could conduct a missile test without warning, according to Reuters.

Chinese President Xi Jingping told Trump in a phone call Wednesday that he wants a peaceful solution to ending North Korea’s nuclear weapons program and would be willing to work with Washington on the matter.

"China insists on realizing the denuclearization of the peninsula ... and is willing to maintain communication and coordination with the American side over the issue on the peninsula," Xi was quoted as saying by state media.

Trump had warned North Korea Tuesday that he vowed to get Kim Jong –Un’s regime under control with or without China’s help.

Meanwhile, North Korea said Monday it would “hold the U.S. wholly accountable for the catastrophic consequences” if there was any further military action after the USS Carl Vinson arrives in the area of the Korean Peninsula.

The Associated Press contributed to this report.

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