Late Tuesday night, the riot police were sent to Hong Kong airport, where they began to clash with protesters.

It was the fifth day in a row that protesters held a demonstration at the airport, which had been largely peaceful.

For two months, there have been nearly daily protests in Hong Kong over China's tightening grip over the island.

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The protests at the Hong Kong airport turned violent late Tuesday night, after the riot police showed up armed with clubs and pepper spray.

Just before midnight, police in riot gear were seen gathering outside the terminals of the world's eighth busiest airport, while protesters started making barriers inside using luggage carts.

Journalists with cameras caught skirmishes beginning to break out between protesters and police, who started using bats and pepper spray to break up the crowds.

Meanwhile, double decker buses were brought in to remove passengers from the airport.

It was the fifth day that protesters had gathered at the airport to demonstrate against the Chinese government, and the second day that flights had been cancelled. But the protests had been largely peaceful up until Tuesday, with little interference from police.

Read more: 'Sorry for the inconvenience': Hong Kong protesters apologized to furious passengers after the city's airport was paralyzed for a second day

But just over the border into mainland China, the Chinese government held drills on Monday, showing off water cannons they seemingly threatened to use against the protesters if they got out of hand.

The protests were initially sparked over a bill that proposed extraditing prisoners to mainland China. Many in Hong Kong thought the bill was a breach of the "one country, two systems" agreement forged when Hong Kong returned to Chinese rule in 1997.

On Monday, the Chinese government said the protests are beginning to show "signs of terrorism."

This story is developing. Check back for updates.