Chief Minister Jayalalitha: Was herself convicted of corruption

A government statement ordering his release said the decision had been taken "purely on humanitarian grounds" in view of Mr Karunanidhi's advanced age.

Mr Karunanidhi told journalists that his release was due to the good will of his supporters.

He also thanked the Delhi government for condemning the action against him.

The dramatic arrest of the 78-year-old politician prompted widespread criticism of the current chief minister, Jayaram Jayalalitha, and strained relations with the central government in Delhi.

Health fears

Mr Karunanidhi was brought out of prison in a wheel chair to be greeted by a huge crowd of supporters.

He had earlier refused to be released on bail, despite growing concern about his health.

His doctor, who examined him on Tuesday, had voiced fears over his high blood pressure and swelling in the legs.

Despite his release, the Tamil Nadu government made clear that the corruption investigation against Mr Karunanidhi would continue.

Calls for action

Mr Karunanidhi is a long-time opponent of Ms Jayalalitha and heads the DMK party, which is a key partner in the ruling coalition in Delhi.

His arrest sparked protests across Tamil Nadu and led to mass arrests of his supporters.

There were calls for tough action by Delhi against Ms Jayalalitha's government.

But the cabinet stopped short of imposing federal rule in the state, issuing a formal warning to Tamil Nadu instead.

The arrest of Mr Karunanidhi was seen by many as an act of revenge by Ms Jayalalitha, who was herself convicted of corruption charges when she was in opposition.

Her party won bitterly contested state elections two months ago, and she became chief minister despite her corruption convictions.