Swu, 67, and 66-year old Muivah, with their wives, are said to have journeyed by road to Dimapur, Nagaland on May 8, after flying in from their hideout in Thailand.

The two leaders of the dominant NSCN faction had earlier come in 1965-66 when they held negotiations with then Prime Ministers Lal Bahadur Shastri and Indira Gandhi.

Union Home Minister L K Advani calling a special meeting tomorrow to discuss the implications of the visit.

The homecoming is being seen as a significant breakthrough in the elusive Naga peace process. The two chiefs are said to be anxious about holding unity talks with the Khaplang faction of the NSCN. The NSCN split in 1988, after which nearly 200 people of the I-M faction were killed by the Khaplang group.

Whether they will hold talks with New Delhi isn't clear. Swaraj Kaushal, the PrimeMinister's principal interlocutor on North-East affairs, said he did not want to comment on their visit but said he had ``discussed substantive issues with the duo earlier and the government was committed to dialogue.''

Since the ceasefire is in operation the security forces are not expected to detain Muivah and Swu.

Officials involved in the negotiations claim that if the two NSCN factions come together, a peace agreement with common demands will be easier to accept and implement. ``We have a generous negotiating brief from the PM,'' says an official, ``Short of sovereignty and some key departments with the Centre, everything else is on the negotiating table.''

During the last round of talks in Amsterdam earlier this year, both Swu and Muivah had been adamant that that they would only hold talks abroad. Earlier, when the two NSCN leaders met Prime Minister Atal Behari Vajpayee in Paris in September last year, they had demanded third-party intervention--a demand which was turned down by the government.