By Charles Haviland BBC reporter in Madras

Police in the southern Indian state of Tamil Nadu have remanded a leading politician in custody for 30 days for his support for Sri Lanka's Tamil Tigers.

Many Tamils in southern India support the Tigers

The leader of the regional MDMK party, popularly known as Vaiko, has been detained under India's Prevention of Terrorism Act (Pota).

The 30 days in custody is extendable to 180 days under the provisions of the act.

In Tamil Nadu, the arrests are widely seen as being intimately linked with the state's highly personalised politics, in particular the rivalry between Vaiko's party and that of Chief Minister Jayalalitha.

The central government in Delhi appears to be in a dilemma as to how to react to the detention.

Awkward for Delhi

Vaiko's party is a junior member of India's governing coalition and ironically, he is the first MP to be charged under the new law.

But a junior minister of state for home affairs in the central government, ID Swamy, said there was no evidence so far that Vaiko had been urging Tamils in south India to join the Tigers and resort to violence.

Jayalalitha is very critical of the Tigers

He said it was possible for the central government to advise a state government if it believed the Pota had been misused

A spokesman for the Bharatiya Janata Party, the main party in the coalition in Delhi, said that the invocation of the act in Vaiko's case was "unwarranted."

"We do not agree with what he says, but many of our allies have made statements with which we do not agree," the spokesman, Arun Jaitley, said.

Sri Lankan concern

The Tamil Tigers have fought a 20-year separatist war in Sri Lanka.

They are also held responsible for the assassination of Indian Prime Minister Rajiv Gandhi in 1991, and are banned in India.

But the arrest of Vaiko - and eight of his party colleagues - is a delicate matter for Delhi.

The Sri Lankan authorities are considering lifting their own ban on the Tigers to pave the way for peace talks, and India's foreign minister has been visiting Colombo to lend support to the island's fledgling peace process.

Vaiko said he had been arrested because of a "political vendetta" against him by Chief Minister, Jayalalitha, whom he called "fascist and autocratic."

Jayalalitha in turn said her government would take steps to ban his party altogether.