The U.S. military flew a B-52 bomber over South Korea on Sunday, in a Cold War-style show of force that was met with concern by human rights campaigners.

American forces made the gesture amid climbing tensions following North Korea's widely-disputed claim that it detonated a hydrogen bomb test on Wednesday.

U.S. Pacific Command announced the flight on Twitter:

[2/4] The B-52 took off from #Andersen AFB, #Guam, and was escorted by @PACAF F-16 and #ROKAF F-15 fighters. pic.twitter.com/5K3rQUdKgZ

— U.S. Pacific Command (@PacificCommand) January 10, 2016

Joe Cirincione, president of the global securities foundation Ploughshares Fund, called the U.S. show of force "counterproductive" and "childish" on Twitter. "This is exactly the kind of nuke macho action we should NOT be taking," Cirincione warned.

North Korea will almost certainly see the flyby as a provocation, but so far has not issued an official response.

The U.S. move follows North Korean leader Kim Jong-un's "victory tour" in the wake of the alleged test. The flight also comes as tensions ratchet up from South Korea, which recently resumed propaganda broadcasts to North Korea.

Many are worried that the U.S. will significantly contribute to the escalation.

The American Friends Service Committee warns in a petition, "In response to this week's reported nuclear test by the North Korean government, the North Korea Sanctions Enforcement Act of 2015 may now advance quickly in Congress. It contains provisions that if enacted will severely restrict the very limited humanitarian operations still underway to assist the people of North Korea."

The group calls on people in the United States to urge their congressional representatives "not to jeopardize humanitarian access to North Korea."

"It's time for a new approach," argued Christine Ahn,  founding board member of the Korea Policy Institute and the National Campaign to End the Korean War, in an article published this week. "What President Obama hasn’t tried yet with North Korea is true engagement. We need our leaders to sit down, talk, and come up with a peace deal that leads to greater security for all of us."

"Many Americans don’t realize that the Korean War, often known as the Forgotten War in the United States, never actually ended," Ahn continued, adding: "The result is intense militarization, recurrent military clashes, and the threat of dangerous miscalculation, which could lead to the annihilation of the Korean peninsula. Moreover, three generations of Korean families remain tragically divided."