President Lee Myung-bak on Monday denounced the weekend beating of a senior police officer by protesters rallying against South Korea''s free trade agreement with the US, saying such violence is a "threat to democracy." The chief of Seoul''s Jongno Police Station, Park Geon-chan, was kicked and punched by protesters during an anti-FTA rally in downtown Seoul on Saturday night. Some protesters also tore away Park''s insignia on his left shoulder, while others stripped Park of his hat and broke his glasses, officials said. One of the attackers, a 54-year-old surnamed Kim, was arrested on Sunday. Kim had previously been questioned by police for throwing a water bottle at a vehicle carrying then US Ambassador Kathleen Stephens during a protest in August this year, police said. "Violence against a uniformed police officer is a threat to democracy," Lee said during a meeting with senior secretaries, according to presidential spokesman Park Jeong-ha. Anti-government activists and critics have staged daily protests in downtown Seoul since Lee''s ruling party-controlled National Assembly approved the trade pact during a chaotic, tear gas-marred session last week, South Korea''s News Agency (Yonhap) reported. Opposition parties have demanded a revision to the deal, claiming it favors the US.