Police in the southern Indian state of Tamil Nadu have arrested a leading politician for expressing support for for Sri Lanka's Tamil Tiger rebels.

The leader of the regional MDMK party, widely known as Vaiko, was arrested as he stepped off a commercial flight in the state capital Madras.

Up to 2,000 MDMK supporters - who are mainly Tamil - were also picked up across the state in a massive overnight operation ahead of his return.

A non-bailable arrest warrant for Vaiko, who has been in the United States, was issued last week under a tough new anti-terrorism law.

Vaiko's party is a partner of Prime Minister Atal Behari Vajpayee's ruling coalition, and correspondents say his arrest by state authorities will cause the federal government considerable embarrassment.

Tamil support

The arrest follows a speech in June that Vaiko allegedly delivered in support of the Tiger rebels, who are banned as a terrorist group in India.

Many Tamils in southern India support the Tigers

"He is still inside the airport but he will be taken to a facility some eight hours drive away," a police official told the AFP news agency.

State authorities said his supporters were arrested to prevent law and order problems following his detention.

Police had already detained eight other senior party officials earlier this week.

The MDMK has always supported the Tiger rebels, who have fought for two decades to create a separate homeland for Sri Lanka's ethnic Tamils.

The Tigers are currently observing a permanent truce in Sri Lanka ahead of expected peace talks with the majority Sinhalese government.

Embarrassment

Correspondents say his arrest may prove awkward for Mr Vajpayee's ruling National Democratic Alliance (NDA).

Jayalalitha is very critical of the Tigers

Mr Vajpayee's government fought hard against strong opposition to ensure the passage of the stringent Prevention of Terrorism Act (POTA).

But the law has now been used by state authorities against a party with two MPs in the national cabinet.

The state ruling party of Chief Minister Jayalalitha was once allied to the NDA but it fell out with the central government and was replaced by a regional rival in the ruling coalition.

As he was being led away, Vaiko said his party would not be cowed by the "fascist rule" of Jayalalitha's AIADMK party.

Vaiko's arrest also comes at a delicate stage of the Sri Lankan peace process and coincides with a visit to Colombo by India's newly appointed foreign minister, Yashwant Sinha.

Authorities in Colombo are considering lifting the ban on the Tigers to pave the way for peace talks, but Delhi remains adamant that it will not do the same.

The rebels are held responsible for the assassination of Indian Prime Minister Rajiv Gandhi 11 years ago.