South Korean authorities have arrested an activist and former leftist politician for praising neighbouring North Korea.

The move to arrest Lee Hwang Sun, leftist politician and a pro-unification activist on Wednesday, comes days after authorities deported another Korean-American woman for the same offence.

Shin Eun-Mi was deported on Saturday for praising North Korea and its leaders at a series of recent lectures she gave with Hwang Sun.

Both women fell foul of South Korea's strict National Security Law (NSL), enacted in 1948 to protect the fledgling state from infiltration by the communist North.

Domestic critics and international rights groups argue that the law is open to abuse and stifles free speech, but officials insist it is justified by the continued threat from the nuclear-armed North.

The Seoul Central District Court said it had agreed to issue the warrant because of "the graveness of the charges" and the likelihood that Hwang, 41, would continue to make similar remarks in the future.

'Anti-state'

The NSL prohibits the spoken or written promotion of North Korean ideology, deeming any such activity to be "anti-state" and subject to up to seven years imprisonment.

Hwang is also accused of making flattering remarks about North Korea on a YouTube channel and writing blog posts praising North Korean founder Kim Il-Sung.

Shin, who co-hosted a number of talk shows with Hwang across the country from October to December, was expelled on Saturday and barred from re-entering the country for five years.

The US State Department responded to her deportation by repeating long-held reservations over the NSL and the limits it sets on freedom of expression in South Korea.

But President Park Geun-Hye, speaking at a New Year press conference on Monday, ruled out any review of the controversial legislation.

"Given our unique situation in which the two Koreas are still confronting each other, we need a minimum level of laws to protect ourselves," Park said.

"So please understand that the related laws are being enforced in line with this situation", she added.

North and South Korea remain technically at war as the 1950-53 Korean conflict ended with a ceasefire rather than a peace treaty.

Source: Agencies