South Korean President Park Geun-hye has fired her chief spokesman over what her office said was a "disgraceful incident" during Park's trip to the United States.

Without elaborating, the presidential Blue House said on its website on Friday that unspecified actions by spokesman Yoon Chang-jung marred the government's dignity.

South Korea's Yonhap news agency cited a police complaint as saying a 56-year-old man grabbed a woman's buttocks in a Washington hotel on Tuesday.

Yoon, who is 56, was not named in the report. Washington's Metropolitan Police Department spokesman Officer Araz Alali said the department is investigating a report of misdemeanour sexual abuse, but he could not comment further.

The Blue House said officials in its embassy in Washington were investigating, but Yoon could not be reached for comment.

Park travelled to Washington seeking a show of unity with her country's top ally at a time of high tension with rival North Korea, which unleashed a torrent of threats against Washington and Seoul in March and April.

Her performance during a joint news conference with President Barack Obama and in a speech to the US Congress won praise in Washington, but her spokesman's firing could cause her political problems in Seoul.

Park, who was inaugurated in late February, faced bitter opposition in her first month on the job to policy proposals and her choices for top government posts, many of whom withdrew amid corruption and other claims.

Yoon, a conservative columnist before joining Park's team last year and becoming spokesman after the inauguration, was disliked by many progressives.

South Korea's political and social landscape is fiercely divided. And Park, who was elected in December, has long faced claims from opponents of being aloof and an "imperial" decision-maker.

She is the eldest child of late President Park Chung-hee, who led South Korea for 18 years in the 1960s and 1970s and is both denounced for human rights abuses and praised as a strong leader.