The police unit known as Operation Fire-for-Fire was supposed to respond in kind, delivering Nigerians from the clutches of armed thugs who sometimes surround entire neighborhoods to rob residents.
Since the unit's debut a year ago, its heavily armed officers have killed dozens of suspected robbers.
They also have slain passersby, churchgoers and others who refused to cough up bribes at ever-present police checkpoints.
Top police officials here recently declared that they would disarm the unit's officers who have fewer than five years of experience in police work to cut down on "accidental killings" of innocent people. The announcement drew no applause from Nigerians, who also find themselves caught in the occasional cross-fire between police and vigilante groups battling for control of the nation's streets.
Nigerians have had more reason lately to be afraid. As Nigeria prepares to hold its first civilian-run elections in 20 years, spiraling violence has gripped the West African nation of 120 million, killing scores of civilians, police officers and, early this month, a leading opposition politician.
Concerned that such violence could imperil national and presidential balloting scheduled between April 12 and May 3, President Olusegun Obasanjo recently warned people against fomenting further conflict. He threatened to "match violence with violence."
"I will send the police, and if the police fail, I will use the army," said Obasanjo, who is seeking reelection. "Anyone who provokes violence will see my red eyes, and my red eyes are not good."
For years, analysts have warned that violence stirred by politicians and organized gangs of criminals stemmed from the same source: the near-total breakdown of law and order in Nigerian society.
In a report released last month, Human Rights Watch documented how vigilante violence posed grave threats to security here in Africa's most populous nation, especially in the run-up to the election. The rights group found that the Oodua People's Congress, a vigilante group based in the country's southwest, had killed or injured hundreds of people during the last few years. Researchers chronicled cases in which OPC members publicly killed and mutilated alleged criminals. The group also has killed police officers.
"Fighting violence with violence will not solve the problem," said Peter Takirambudde, who heads the Africa division of Human Rights Watch, which called on the Nigerian government to maintain law and order in the weeks preceding the election.
Analysts agree that the line between political violence and street crime is often blurred because politicians and other influence peddlers use hired thugs -- and police officers -- as private armies. Often the people who assassinate politicians are also the criminals who terrorize neighborhoods, robbing and killing their victims in broad daylight.
In several states, vigilante groups -- which draw their members from a huge pool of angry, unemployed youths -- perform the functions of police and even battle to keep officers out of their areas.
"It's easy for people with power to use these young men," known here as area boys, said Carina Tertsakian, a Human Rights Watch researcher who has written several reports on violations in Nigeria. "Powerful men give these youths a little money and weapons, then they're at their service."
Restoring law and order was a major task facing Obasanjo when he was elected in 1999, ending 15 years of uninterrupted military rule.
Obasanjo, who as a general led Nigeria in the 1970s during an earlier military regime, ordered law enforcement leaders to help bring an end to armed banditry and political violence, estimated to account for more than 10,000 deaths since 1999. The top federal police officer, Inspector General Tafa Balogun, launched Operation Fire-for-Fire last year, and officers received the green light to shoot suspected robbers on sight. Police said they adopted the strategy partly to reduce their own casualties.
"Since the number of robbers is increasing like ants and they take joy in killing police officers, police have decided to adopt this measure not only to drastically reduce the growing number of robbers but also to save the lives of policemen," said a police spokesman in Lagos, a port city and the nation's commercial capital.
The new anti-crime offensive brought immediate results: Within a two-week period last March, police shot dead 23 suspected armed robbers. But civilian casualties also mounted.
Several churchgoers who refused to pay bribes at a police checkpoint, citing religious reasons, were gunned down. On another occasion, police shot and killed five people they believed were criminals. Families of the dead said later that their relatives were victims fleeing from robbers.
"They are no different from the other policemen, maybe more brutal," said Joseph Kanu, who operates a minivan taxi business in Lagos. "All they do is mount roadblocks and extort money. If you don't pay them, they use their guns on you."
After several civilians were killed and injured by officers attached to Operation Fire-for-Fire, the governor of Anambra state threatened to reintroduce his Bakassi Boys vigilante group, which was condemned by human rights groups for decapitating scores of suspected criminals before setting the bodies ablaze. A few months earlier, Obasanjo ordered police to disband the Bakassi Boys after the group was accused of targeting political opponents of the state government.
"Harsh measures such as Operation Fire-for-Fire only encourage human rights violations by the police," said Tertsakian, the Human Rights Watch researcher. "It's very discouraging to see that Nigerian leaders don't seem to understand what's wrong with [advocating] such violence."
Obasanjo's threat to "match violence with violence" came after opposition politicians accused his ruling party of orchestrating the March 5 attack on Marshall Harry, who was fatally shot when gunmen broke into his home in Abuja, the capital.
Harry had bolted the ruling party to run the campaign of former military ruler and retired Maj. Gen. Muhammadu Buhari, whose All Nigeria People's Party is expected to provide stiff opposition to Obasanjo. The president has denied that his People's Democratic Party played a role in Harry's killing.
Tertsakian said that unlike Harry's killing, which was widely reported across Nigeria, recent deaths of scores of local politicians have gone largely unreported.
Tertsakian and other analysts say Harry's killing could presage more bloodletting.
"I do not want to be pessimistic, but sadly we're going to see more violence," said Salih Booker, director of Africa Action, a nonprofit advocacy group in Washington. "People have been doing it with impunity, and the government has not made it clear in any way that these acts will not go unpunished."
Special correspondent Dulue Mbachu contributed to this report.