A chartered plane carrying some 300 South Koreans, who were detained in a large-scale US immigration raid at a battery project site in Georgia, landed at Incheon airport near Seoul on Friday.

Their return capped a week of intense negotiations by Seoul to win their release and bring them home after they were taken into custody in handcuffs and shackles – shocking many in South Korea, a key US ally.

South Korea later said it has a reached an agreement with the United States for the Korean workers’ releases.

South Korean businesses have long struggled with getting proper visas for specialist workers needed at project sites for months at a time, which has led to some workers relying on grey areas in US visa enforcement.

The two countries are looking at establishing a working group to consider a new type of visa for Koreans, according to South Korea's foreign minister who visited Washington this week.

The plane also carried 10 workers from China, three from Japan and an Indonesian national.

The workers had been held at an immigration detention centre in Folkston, 460 kilometres southeast of Atlanta.

After their releases from the detention centre, they were transferred to Atlanta to board the charter plane. (Agencies)