Seoul (AFP) - South Korea's presidential Blue House said Wednesday it was "regrettable" a government-backed concert for US troops stationed in the country was hit by a boycott from scores of K-Pop stars.

The Sunday concert was to mark the 100th anniversary of the US 2nd Infantry Division, which is stationed in Uijeongbu, just north of the capital Seoul, but activists launched a campaign against the event.

They argued it coincided with the 15th anniversary of the deaths of two South Korean high school girls, who were crushed to death by a US military vehicle near Uijeongbu, sparking nationwide protests at the time.

Scores of top K-Pop musicians scheduled to perform, including singer Insooni, K-pop bands EXID, Oh My Girl, Sweet Sorrow, punk band Crying Nut and rapper SanE, failed to show up or left the stage before performing.

"I'm sorry but I can't sing under these circumstances," Insooni told the audience at the start of the concert, before walking off stage.

Only a few acts -- including a US Army Band and a Korean traditional music ensemble -- actually made their scheduled performances.

"We find it regrettable that the event prepared as a token of gratitude and farewell has been disrupted," spokesman Yoon Young-Chan of the presidential Blue House said Wednesday.

The US 2nd Infantry Division was the first US military unit that was sent to help defend South Korea at the start of the Korean War and it is set to be relocated further south to Pyeongtaek City next year, he said.

The Blue House comment came hours after the country's new president Moon Jae-In visited General Vincent Brooks, head of the US-South Korea Combined Forces Command, to stress the "rock solid" alliance between the two countries.

Moon will visit Washington later this month for his first summit with President Trump since the left-leaning South Korean president was sworn in early May.

Uijeongbu City mayor Ahn Byung-Yong issued a public apology on Monday over the episode, blaming "some activists and leftist media" who "viciously" attacked singers and their agents for their involvement.

South Korea hosts about 28,500 US soldiers and has a defence treaty with the United States.

The US presence in the country is welcomed by the majority of the public, but rare instances of crimes or accidents committed by US service people have triggered protests.