Seoul (AFP) - Elderly men in South Korea have allegedly been given erectile dysfunction drugs to buy their votes in legislative elections, prosecutors said Tuesday, announcing an investigation into the suspected breach.

South Koreans go to the polls on Wednesday in an election already overshadowed by North Korean nuclear threats and economic difficulties.

The alleged vote-buying took place in Suwon, 30 kilometres (around 20 miles) south of the capital Seoul.

"We have yet to verify the allegations. If confirmed, this could constitute a breach of election law," the spokesman for Suwon Prosecutors' Office told AFP.

Vote-buying in South Korea carries a sentence of up to five years in prison or a fine of 10 million won ($8,750).

Erectile dysfunction drugs are a prescription medication in South Korea and prosecutors will investigate how the unnamed candidate was allegedly in possession of so many, the Dong-A Ilbo daily said.

Anyone found guilty of vote-buying risks being stripped of their election victory, while voters face fines of up to 50 times the value of the cash or gift they received in return for supporting the candidate.