By Senan Murray
BBC News website, Abuja
Many men angry at poverty and pollution have picked up guns
More than a year since they began their armed campaign in Nigeria's volatile Niger Delta, the Movement for the Emancipation of the Niger Delta (Mend) remains a shadowy and faceless group.
If they had hoped to mend the region, which has been torn apart by violence and wrecked by pollution from oil exploration, they do not seem to have made a huge success of it.
Instead, their campaign has heightened tension in the area and is threatening to cripple Nigeria's crude oil export industry.
Experts predict that if the violence continues, oil companies operating in the area will be forced to leave, sending Nigeria's economy into a nosedive.
Should that happen - and it is beginning to look possible with increased kidnappings and pipeline bombings in the area - Mend would have succeeded in their campaign to bring Nigeria's oil-dependent economy to its knees.
"They have decided to step up their attacks to keep the Niger Delta on the front burner so that the incoming administration in Nigeria will not lose sight of its seriousness," says Benjamin Akande, a US-based expert on Nigeria.
Formed early 2006
Close links to militant Mujahid Dokubo-Asari's Niger Delta Volunteer Force
Split into two rival groups late 2006
Bayelsa State faction leader - Jomo Gbomo
Delta State faction leader - Gen Godswill Tamuno
Demand 100% control of Nigeria's oil wealth
Demand release from jail of Dokubo-Asari being tried for treason
Demand release of impeached Bayelsa governor on trial for money laundering
Operate from creeks of Niger Delta
Communicate with media by e-mail
President Olusegun Obasanjo who has made unsuccessful attempts to end the violence in the region stands down in two weeks following last month's elections won by the governing party's Umaru Yar'Adua.
Mend's success at arm-twisting government and rich Western oil companies into parting with huge ransom payments in exchange for abducted foreign workers has spawned copycats in the troubled region.
Indeed, insiders say the emergence of a splinter group from Mend is a result of disagreements over the sharing of ransom takings, a charge often denied by the group.
While Jomo Gbomo, founding leader of the militant group remains in charge of his group in the Bayelsa State and Rivers State creeks, a person calling himself Gen Godswill Tamuno has emerged claiming to be the leader of another Mend group in Delta State.
"How can I be called a factional leader and compared to political thugs in Delta State who dare not sit in my presence?" Mr Gbomo queried in an angry email to the BBC.
"I am the overall leader of all militant groups in the Niger Delta. That has never been in dispute."
Other groups have also emerged without any clear political agenda, attracted by the lucrative business of hostage taking.
With names like the Coalition for Military Action in the Niger Delta (Coma), the Joint Revolutionary Council (JRC), the Niger Delta Vigilante and the Martyrs Brigade, these groups have all claimed responsibility for abductions and attacks in the region.
'Press release response'
But Mend appears to be the only active militant group with a clearly articulated political goal: greater control of Nigeria's oil wealth which comes from the swamps of the Delta.
Mend want Nigerian separatist leader Mujahid Dokubo-Asari freed
It also has a modern approach to the media, sending photos of hostages as well as e-mailing regular statements confirming their operations.
Although Nigeria is Africa's largest producer of crude oil, most of its citizens live in abject poverty, particularly in the Niger Delta where oil exploration has destroyed farmlands and thrown local fishermen out of work.
Mend says all this must change and to press home their point, they have taken up arms against the Nigerian central government which appears helpless.
"The Nigerian government must move on from press release responses and really deal with these attackers because so far we have seen nothing happening," Mr Akande told the BBC News website.
"You either sit down with them and resolve this issue or you go in and deal with them squarely if you are convinced that you are justified."
From a poorly organised gang fighting with little more than sticks and machetes, Mend has grown to become a disciplined military machine, using speedboats, machine guns and rocket-propelled grenades to carry out precise attacks on oil targets.
Mend send e-mails and photos of hostages to the media
Mend's attacks have been the main cause of an 800,000 bpd (25%) reduction in Nigeria's oil production output, according to Finance Minister Nenadi Usman.
Some Niger Delta analysts say Mend sprang out of ethnic-based Ijaw group the Niger Delta Peoples Volunteer Force (NDPVF), which was outlawed in 2004 after it declared an "all out war" against the Nigerian government.
The threat forced the Nigerian government to open negotiations with the NDPVF, but a year later its leader Mujahid Dokubo-Asari, 42, was arrested and charged with treason.
But Mr Dokubo-Asari's arrest and the government's ban on his organisation gave birth to Mend, believed to be led by university-educated young Nigerians.
And unlike Mr Dokubo-Asari's centralised NDPVF, Mend appears to have fairly broad support across the Delta region, a factor that helps keep the identities and the whereabouts of its leaders secret.
Although the group regularly attacks oil installations, their predominant tactic remains the kidnapping of foreign workers whom they usually release unharmed after they feel they have made their point, says the BBC's Abdullahi Kaura.