A South Korean official who suggested the country "import young women" from "Vietnam or Sri Lanka" to boost its birth-rate has been expelled from his party.

Kim Hee-soo, the head of the southern Jindo County, said the woman could be married off to "young men in rural areas" during a town hall last week.

The suggestion comes as South Korea continues to grapple with the lowest birth-rates in the world, which could see the country's 50 million-strong population drop by half in 60 years.

But Kim's statement, which was televised, did not go down well - triggering a diplomatic protest from Vietnam, days of public anger and his expulsion from the ruling Democratic Party.

Attempts by Kim to defuse the outrage with an apology a day after the town hall appear to have failed.

The town hall had been called to discuss a potential merger between the province where Jindo County is located and a nearby city - something regions with shrinking populations are looking at for administrative reasons.

Kim said his comment had been intended to highlight population issues in rural regions but admitted the language he had used was "inappropriate", local media reported.

South Jeolla Province also issued a formal apology for Kim's "inappropriate remarks", which it said "has caused deep pain to Vietnamese people and to women", local media reported.

The Vietnamese Embassy in Seoul had condemned Kim's remarks, saying in a statement on Facebook that his words were "not simply a matter of expression but a matter of values and attitudes towards migrant women and minority groups".

Sri Lanka authorities have not publicly addressed the controversy.

The Democratic Party's Supreme Council had voted unanimously to expel Kim, a party spokesperson told reporters on Monday.

Meanwhile, activists for women and migrant rights are reportedly planning to hold a rally in front of Jindo County Office on Tuesday over Kim's comments.