Trump arrived in Seoul earlier in the day following his trip to Osaka, Japan, to take part in the Group of 20 summit. The US leader later attended a welcome dinner hosted by South Korean President Moon Jae-in and his wife, Kim Jung-sook, at the presidential office Cheong Wa Dae. Trump and Moon will hold a bilateral summit on Sunday.

In a rally organized by supporters of former conservative President Park Geun-hye, a participant wearing a Trump mask went onto a makeshift stage set up in front of Deoksu Palace in central Seoul and sang the national anthem of Korea. And then the US national anthem was played with the giant television screen showing footage from Trump's inauguration ceremony.

They saluted in unison when the host said, "Let's salute President Donald Trump of the United States of America that protects the free Republic of Korea." Some of the participants were holding banners reading, "Thank you America."

The US fought alongside South Korea under the United Nations flag against an invasion by North Korea, which was backed by China and the Soviet Union, during the 1950-53 Korean War. More than 36,000 US troops were killed in the war.

The group had its main welcoming ceremony for Trump in the evening after holding a separate rally against the impeachment of former President Park.

Our Republican Party, a far-right minor opposition party, held a similar rally in front of the Seoul Station. 

Holding banners reading, "South Korea and the United States are a blood alliance" and "We welcome President Trump's visit to South Korea," the participants chanted slogans calling for an immediate release of the jailed Park and a stronger alliance between the two countries.

The party, previously the Korean Patriots Party, was established in July 2017 by supporters of Park, who was ousted from office in March of that year over a corruption scandal.

Progressive civic groups held their own rallies in the downtown Gwanghwamun area to oppose Trump's visit here.

"We don't welcome the South Korea visit by President Trump, who threatens peace on the Korean Peninsula and in the rest of the world," one of the groups said in a statement released ahead of its rally set to begin at Seoul Plaza in front of Seoul City Hall at about 5 p.m. "We denounce Trump, who enforces sanctions against North Korea and interferes with its internal politics."

The rally drew 1,500 participants, who later marched from Seoul Plaza to nearby Jonggak subway station while calling for an end to US and international sanctions against North Korea. (Yonhap)