SEOUL (AFP) - South Korean prosecutors said on Tuesday they had decided to charge the former head of the country's spy agency with meddling in last year's presidential election.

The decision follows an official investigation into allegations that Won Sei-Hoon, as director of the National Intelligence Service (NIS), had ordered agents to post stories and comments attacking the opposition presidential candidate on popular websites.

The candidate, Moon Jae-In, was defeated in the December 19 vote by the conservative favourite and current president, Park Geun-Hye.

The prosecutor's office said that while Won would be indicted, it would not seek to have him placed in custody pending trial.

Won headed the NIS for about four years until early 2013.

The prosecution office said it had also decided to bring charges against Kim Yong-Pan, the former head of the Seoul Metropolitan Police Agency, for obstructing the police probe into the case.