[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/08/05/art.bush.south.korea.jpg caption="President Bush walks with South Korean Foreign Minister Yoo Myung-Hwan."]
SEOUL, South Korea (CNN) - Thousands of protesters packed the streets of the South Korean capital Tuesday as President Bush arrived for the start of his Asian tour.
While some of the demonstrations were peaceful, violence erupted at other protest sites. In one instance, riot police fired a water cannon to keep the crowds at bay.
Police said they detained about 80 protesters. They estimated about 2,700 people were participating in the protests, which included a candlelight march and a sit-in. But the organizers said some 10,000 were taking part in the demonstrations.
Bush's week long trip to the region is his ninth visit as president. His stop in Seoul comes just a few months after violent street protests erupted over worries about the safety of U.S. beef imports.
While those tensions seem to have eased, the United States' nuclear disarmament deal with North Korea is also a concern.
Michael Green, a former Bush adviser on Asian affairs, and now with the Center for Strategic and International Studies, says Seoul's proximity to North Korea contributes to an ongoing unease.
"The North Koreans have 11,000 artillery tubes and rockets aimed at the South Korean capital, so any little thing that we do with North Korea makes the South Koreans very jittery," Green said.
He added, "On the other hand, the U.S. has to worry a great deal about where terrorists might get nuclear weapons or nuclear material."
After South Korea, the president will go to Thailand for what's being billed as a major Asia policy speech.
He's expected to denounce the military regime in neighboring Myanmar –also known as Burma - for its human rights abuses. First lady Laura Bush has fervently taken up the cause, and last May sharply criticized the regime for its response to a May cyclone that killed tens of thousands of people.
"The more I've seen, the more critical I see the need is ... for the world to pay attention to the people of Burma, and for the world to put pressure on the military regime," Mrs. Bush told reporters in a historic news conference in the White House briefing room - the first ever by a first lady.
President Bush will continue his Asia tour with a visit to Beijing to attend the 2008 Olympics, a decision critics have blasted, saying his presence gives China a pass on its poor record on human rights and religious freedom.
Last week, the president again defended his decision in an interview with China's state-run television network. "I think it's best for U.S.-China's relations that I go. I know it's important for me to send a clear signal to the Chinese people that we respect them," he said.
Bush plans to attend a church service in Beijing to deliver what is sure to be a carefully crafted message.
"He will have to say something public which is always tricky, how much he spotlights these issues," Green said. "And I think he will not (do it) in an adversarial way."
Last week, the president welcomed five Chinese dissidents to the White House, telling them he would carry a "message of freedom" to Beijing. The move drew a sharp rebuke from Chinese leaders, who accused the president of interfering with China's internal affairs.