South Korea's Constitutional Court ruled Thursday that the country must allow alternative social service for people who conscientiously object to military service, which is currently mandatory for able-bodied males.

The ruling requires the government to introduce alternative service by the end of 2019. It was hailed by activists as a breakthrough that advances individual rights and freedom of thought.

It is also likely to trigger a heated debate in a country which maintains a huge military to counter North Korea threats, and where many have accused conscientious objectors of attempting to evade the draft.

Hundreds of conscientious objectors are imprisoned in South Korea each year, serving terms of 18 months or longer. Most are Jehovah's Witnesses who refuse to serve in the military on religious grounds.

"Too many people have been forced to choose between prison and the military, and when they choose prison, a term of 1 1/2 years has been almost automatic," said Lim Jae-sung, a human rights lawyer who has represented contentious objectors. "This is great news for those who are currently on trial or will conscientiously object to military service in the future as we probably won't be marching them straight to jail."

The court said the current law, which does not permit alternative service, is unconstitutional because it infringes excessively on individual rights.

The court acknowledged that conscientious objectors experience "enormous disadvantages" in addition to their prison terms, including restrictions in public sector employment, maintaining business licenses and social stigma.