By Alex Jensen

SEOUL

More than 20,000 South Korean police officers scrambled to contain tens of thousands of protesters in rainy central Seoul late Saturday as clashes threatened to spill out of control.

The rally brought together 53 labor unions and civic groups -- police estimated a total of 80,000 protesters, though estimates ranged as high as 130,000 -- in opposition to a series of government policies, including the recent move to reintroduce state-published history textbooks from 2017 onwards.

Officers barricaded Seoul’s iconic Gwanghwamun Square, deploying temporary walls, water cannons and tear gas.

Amateur social media footage appeared to show students struggling to breathe in a stairwell of Gwanghwamun’s subway station after being sprayed by police, with state news agency Yonhap so far reporting 11 arrests.

While heavy-handed policing was reminiscent of an anti-government May Day rally earlier this year, the gathering marked the country’s biggest protest since 2008 -- when public uproar due to concerns over mad cow disease and American beef imports brought Koreans onto the streets.

Local authorities warned that tough measures would be taken to clamp down on any violence, while teachers were warned that they were forbidden from participating.

It was not immediately clear how many protesters or police had been hurt, nor how many of the 700 police vehicles dispatched to the scene were damaged.

Officers were determined to prevent the rally from moving to the nearby presidential office.

President Park Geun-hye herself departed for Turkey earlier in the day ahead of next week’s G20 summit.

A Gallup Korea poll this week showed that Park’s approval rating of 40 percent represented a near three-month low following last week’s history textbook announcement.

The last South Korean president to oversee such a policy for secondary school students was Park’s own father in the 1970s.