The political turmoil following last week’s martial law crisis in South Korea has heightened tensions in the US military forces stationed in the country, with some units imposing travel restrictions and curfew, according to officials Monday.

A sergeant first class at the US Forces Korea's headquarters of Camp Humphreys, a key US military base in Pyeongtaek, about 65 kilometers south of Seoul, told The Korea Herald that the USFK issued a new regulation limiting all service members' travel to Seoul and surrounding metropolitan cities after Yoon abruptly declared martial law at 11 p.m. on Dec. 3.

"Only KATUSA (Korean Augmentation to the United States Army) soldiers whose homes are in Seoul are allowed to travel to Seoul," said a US service member who wished to remain anonymous.

"A new curfew was also implemented, requiring all soldiers to return by 11 p.m. when going out."

The USFK also warned the soldiers against gathering in highly congested areas near the base, he added.

“We were advised not to visit neighborhoods like Anjeong-ri, on the perimeter of Camp Humphreys, and Sinjang-dong, where Osan Air Force Base is located.”

The measures came in line with the warning messages from the commander of US Forces Korea on Dec. 5, two days after South Korean President Yoon Seok Yeol abruptly declared martial law, citing the need to protect the country from "anti-state" forces.

"I ask everyone to exercise individual vigilance about where, how, when, and with whom you will travel throughout Korea," USFK Commander Gen. Paul J. LaCamera said in a statement released on the command's website.

"The events of last night (on Dec. 3) are not over as the government of the Republic of Korea is working through their democratic processes to address the concerns of its citizens and resolve their disagreements in accordance with the rule of law," LaCamera said.

The USFK will decide whether to lift or strengthen the restrictions on Dec. 11 after reviewing the political situation, sources said.