The terrorist attacks in the northeast are the most serious in recent years, killing at least a hundred people and maiming scores of others.
Who are the terrorists operating in India's seven northeastern states?
G Vinayak provides a primer to the terrorist groups in the northeast.
India's northeast has the dubious distinction of being home to Asia's longest running insurgency.
The Nagas led by A Z Phizo launched an insurrection against the newly-formed Indian nation way back in 1956.
Since then the Naga insurgency has spawned dozens of similar protests across the region that still remains on the periphery of national consciousness.
Each of the seven states in the region today has some insurgency or the other keeping the state busy, often dominating and
setting the agenda in the respective geographical area.
At last count there were at least 15 major groups in the region that have been banned by the Centre. If you take the smaller groups, the number is closer to 40.
Over the last decade, at least 11,000 people, including security forces, civilians and militants, have been killed in insurgency-related violence in the four major states of Assam, Manipur, Nagaland and Tripura.
A majority of these outfits were formed in the 1980s or early 1990s but each of them is an offshoot of earlier attempts to rebel against the Indian State.
Except the Naga insurgency, most of the outfits in the northeast have been born out of neglect heaped upon by New Delhi on these distant states since Independence.
There are others who regard these insurgencies as nothing but money-making enterprises.
Says a senior army officer, who spoke on condition that he would not be identified in this report: "Insurgency is the biggest business in the northeast. Most of these groups exist only to make money through extortion and kidnappings. Ideology has taken a backseat."
Going strictly by numbers, Assam continues to bleed because of insurgency-related violence.
In 2003, over 400 people were killed in militant violence. Among the killed are a large number of militants (208) while 103 civilians died during the same period. These figures are more or less in keeping with the trend in 2002 when 445 people lost their lives in Assam. Among them were 275 militants.
Formed in 1979, the United Liberation Front of Asom became a force to reckon with in the late 1980s. It virtually ran a parallel government in the state between 1988 and 1990 till New Delhi cracked down by ordering full-fledged army action.
Operation Bajrang was followed by Operation Rhino.
More than a decade after these two military operations, ULFA remains active despite a split in its ranks and surrender of a large number of its cadres over the years.
The National Democratic Front of Bodoland was formed by group of radical Bodo youth on October 3, 1986 who, like their counterparts in ULFA, believe their nationalities can prosper only when outside the Indian State.
The NDFB is active in Assam's Bodo-dominated areas bordering West Bengal and Bhutan.
By exploding bombs across the state and in Nagaland, both ULFA and NDFB are out to prove that they are still a force to reckon with despite having being evicted from Bhutan last December.
At least two divisions of the army (20,000 troops), over 10,000 paramilitary personnel besides 50,000-odd Assam policemen remain engaged in battling ULFA, and to a lesser extent NDFB.
As of today, Manipur is the worst case scenario in the northeast as far as militancy is concerned. Apart from the fact that there are more militant groups in the state than anywhere else -- at least seven prominent groups operate in Manipur -- the rivalries between these outfits often leads to greater violence.
Kidnappings and killings are common in Manipur.
What worries the security forces is the parallel government run by militant groups. These groups extort money or levy 'taxes' on people, government officials and businessmen.
No transporter can operate in Manipur without having paid at least three prominent militant groups.
The outfits dispense instant justice, provide protection and rule certain areas with impunity.
Some of the groups like the Kanglei Yaol Kanba Lup are attempting to 'cleanse' Manipuri society by launching high-profile campaigns against drug peddlers, corrupt government officials and issuing diktats to 'preserve' Manipuri culture.
The state with the oldest running insurgency, Nagaland appears to be as normal as any other Indian state following the ceasefire between the Isak-Muivah group of the National Socialist Council of Nagaland (NSCN-IM). But factional fights between the IM group and its rival the S S Khaplang-led NSCN(K) has dominated the scene over the past few years.
The NSCN(IM) is regarded as a mentor of many groups in the northeast since it helped form these outfits, nurtured and armed them over the years. But it has created tensions in the northeast by demanding a 'greater Nagaland' by uniting Naga-inhabited areas spread over other states like Manipur, Assam and Arunachal Pradesh.
One of the most violence-prone states, Tripura has been traumatised by killings and kidnappings over the past decade. Two major outfits, the National Liberation Front of Tripura and All Tripura Tigers Force have been on the rampage, killing and kidnapping people with impunity.
Tripura, which was a princely state before Independence, has witnessed a steady decline of its indigenous population giving rise to militancy among the tribals. Tripura has nearly 10 lakh (a million) indigenous tribals who live in abject poverty in the hilly and often inaccessible areas of the state.
The two banned militant groups -- the ATTF and the NLFT -- have bases in Bangladesh across the porous international border.
Among the other states in the northeast, Meghalaya has two active insurgent groups. Arunachal Pradesh and Mizoram are relatively free of militancy but security experts warn that trouble is round the corner in Arunachal Pradesh where the NSCN(IM) is making inroads in some districts.
Mizoram is perhaps the only state in the region which can claim to have abandoned insurgency. Indeed, the Mizo National Front, which was underground for 20 years, signed a landmark pact in 1986, came overground and now runs the state government.
The major militant groups in the northeast which have been declared as 'unlawful organisations' under the Unlawful Activities (Prevention) Act, 1967 include:
The United Liberation Front of Asom.
The National Democratic Front of Bodoland.
The People's Liberation Army.
The United National Liberation Front.
The People's Revolutionary Party of Kangleipak.
The Kangleipak Communist Party.
The Kanglei Yaol Kanba Lup.
The Manipur People's Liberation Front.
The Revolutionary People's Front.
The Hynniewtrep National Liberation Council.
The Achik National Volunteer Council.
The National Socialist Council of Nagaland including all factions.
The All Tripura Tiger Force.
The National Liberation Front of Tripura.
Image: Rajesh Karkera