India's north-eastern state of Assam is a veritable tinder-box. So why does it periodically erupt into violence and blood-letting?
The latest bout has left about 40 dead and displaced tens of thousands. The state remains tense as the army has been issued with "shoot on sight" orders.
At the heart of Assam's troubles is a debate over so-called "infiltration" by outsiders, which has led to ethnic tension between the state's indigenous population and Bengali migrants.
Changing demography, loss of land and livelihood and intensified competition for political power has added a deadly potency to the issue of who has a right to Assam.
The migrants say they are mostly descended from East Bengali Muslims brought to Assam by the British to boost agricultural output by taming the "Chars" (river islands) - and that they are as Indian as the ethnic Assamese or the tribespeople in the state.
But the others do not accept that argument and groups representing them say more and more poor peasants from Bangladesh are flooding Assam, taking advantage of a porous riverine border.
The worst violence prompted by such tensions erupted during a controversial election in February 1983 - nearly 3,000 people were left dead in that episode.
The indigenous Assamese were joined by many local tribal groups in opposing the state assembly elections because they alleged that the electoral rolls were full of "infiltrators" - the expression locally used to describe illegal migrants from neighbouring Bangladesh.
It came after four years of a determined campaign to drive out the migrants, hundreds of whom were killed in the village of Nellie in central Assam that February.
After the 1983 elections, India's federal government tried to placate local sentiments by signing an accord with the All Assam Students Union (AASU) in 1985 which was leading the campaign against the migrants.
The accord promised to disenfranchise migrants who came after 1966 for a period of 10 years, after which they would be included in electoral rolls.
The hardline Assamese described the 1985 accord as a "betrayal" and decided to wage an armed campaign against India.
Twenty years later, a faction of the separatist United Liberation Front of Assam (Ulfa) is negotiating with Delhi, asking for more concrete protection for indigenous populations against what they describe as "relentless illegal migration from across the border".
Groups representing Bodo, Rabha, Tiwa and other tribespeople support the Ulfa's call for stopping illegal migration and protecting the lands and livelihoods of the local populations.
Delhi has reportedly promised a replay of the 1985 Assam accord - disenfranchisement of the migrants who came between 1966 and 1971 for a period of 10 years, but not much more.
The latest clashes have affected four districts of western Assam, where the migrants - or their descendants from East Bengal (now Bangladesh) - are pitted against tribespeople such as the Bodos, Rabhas and Garos.
In Kokrajhar, the Bodo heartland, Muslim migrants are regularly attacked by Bodo separatist rebels and this periodically erupts into full-scale riots.
More than 100 migrants were killed in one such raid at Bansbari, a makeshift camp for displaced Muslims in 1993.
The Bodos now have an autonomous territorial council which one of their parties, the Bodoland People's Front (BPF), controls. But many feel migrants have taken over much of the land they traditionally occupied.
The migrants and their descendants have also become more assertive with the formation of the Assam United Democratic Front which seeks to protect the rights of minorities and their periodic ousting from settlements through violence.
The Front, led by a charismatic religious leader Maulana Badruddin Ajmal, has increased its tally in the state legislature over the last two state elections.
In 2011, it emerged as the main opposition to Assam's ruling Congress party, winning three times the number of seats won by regional Assamese parties and the Hindu nationalist BJP.
Four years ago, different local tribes people and ethnic Assamese were involved in bitter rioting in the district of Darrang, in which the army had to be called out to stop the blood-letting.
Trouble in Assam is not simply a regional issue - the violence has also affected railway traffic between India's mainland and its north-eastern states because violence-torn Kokrajhar district sits in the "chicken neck", the strategically vital corridor that connects the north-east to the rest of the country.
Subir Bhaumik is an independent journalist and writer based in Calcutta