Ties between Tokyo and Seoul have long been soured by the sex slave issue, a legacy of Japan’s colonial rule over the Korean peninsula and of the war.

Abe told reporters in Tokyo on Monday that Japan has apologised and expressed its remorse, but added future Japanese generations should not have to keep on doing so.

“We should never allow this problem to drag on into the next generation,” he said, echoing remarks he made marking the 70th anniversary of the end of World War Two on August 15. “From now on, Japan and South Korea will enter a new era.”

Some on Japan’s conservative far right have long said the country has nothing to apologise for and have questioned the accounts of the surviving comfort women, suggesting they were prostitutes and not coerced.

Demonstrators, mostly in their 60s or older, sang “Kimigayo,” the national anthem which is an ode to Japan’s emperor, and carried red and white national flags.

“We will never allow this quislingism,” participants at the rally outside the compound housing Abe’s official office and residence chanted in unison, calling him a traitor.

“Reverse this disgraceful act,” they yelled.

“Abe, you stained the spirit of the war dead!” one woman shouted.

“You must commit seppuku,” she added, referring to the traditional act of ritual suicide by disembowelment.

Satoru Mizushima, a rally organiser, said: “The agreement is going to be Japan’s worst blemish. Prime Minister Abe did what he should not do. It was so deplorable.”

The crowd then moved to the foreign ministry for a similar rally.

Additional reporting by Reuters