Anti-government protesters broke into the compound of a police sports club on Sunday where Thai Prime Minister Yingluck Shinawatra had been during the morning, but she was able to leave the premises and went to an undisclosed location, an aide said.
In another area of the city, police fired three rounds of teargas at protesters near Government House, where Yingluck's office is, a Reuters witness said, as demonstrators seeking to overthrow her government massed in areas across the city.
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Two knives were found at the scene in Islington, North London, and the suspects fled on foot before being arrested.
The violence began after a counter-protester allegedly doused a female rally organiser with pepper spray.