An article from the Korean Herald

Korea arrests 157 in protest against US ..

Korean police hosed protesters with water laced with blue dye and mobilized specially-trained plainclothes officers to break up an anti-government demonstration late Friday and early Saturday, witnesses were quoted as saying by AFP.

The Seoul Police Agency said it had arrested 157 people on charges of
staging illegal demonstrations in central Seoul. There were no immediate reports of injuries.

Some 5,500 people showed up for the 100th candle-lit rally to protest
against South Koreas resumption of US beef imports and against policies of
President Lee Myung-Bak of the conservative Grand National Party, police said.

They chanted Lee Myung-Bak Out! and Renegotiate the beef deal, witnesses said.

Police sprayed water mixed with blue dye at demonstrators and arrested
offenders whose clothes were tainted by the pigment after the crowd dispersed into neighbouring streets and alleys, witnesses said.

Police also brought in plainclothes officers, who are specialized in
chasing and overpowering offenders during street protests.

Such personnel, although used widely by past authoritarian governments,
have been seldom seen in the street during the past 10 years of liberal rule.

Koreas April decision to resume US beef imports sparked months of
street protests. Because of fears over mad cow disease, Seoul suspended US beef imports in 2003.

The rallies largely subsided after Seoul secured extra health safeguards
for US beef imports.