Beware of police roadblocks in Nigeria: If you cannot pay a bribe, you can end up dead, according to an Amnesty International report published Wednesday.

It highlights a new danger in a country regularly denounced as one of the most corrupt in the world, where bribe-taking long has been a way for poorly paid government workers to make ends meet.

Nigeria's police force is poorly paid and trained, and short of essential tools including bulletproof vests, fuel, even paper and pens, Amnesty said. But there appears to be no shortage of the bullets its officers use to kill people they are supposed to protect, the report said.

"In a country where bribes guarantee safety, those who cannot afford to pay are at risk of being shot or tortured to death by the police," it said.

Emmanuel Ojukwu, the national police spokesman, told The Associated Press that "extrajudicial killing is not approved in Nigeria."

He said officers who use unlawful force are arrested, prosecuted and sanctioned. But he could not say how many officers have been dismissed or jailed.

Amnesty International said its research, conducted over three years, indicates officers suspected of unlawful killings are "sent on training" or transferred to other areas. It said there are few prosecutions and it condemned a "culture of impunity."

No one can say how many people are summarily killed by Nigerian police, but the report put it at hundreds each year.

"Many unlawful killings happen during police operations. In other cases, the police shoot and kill drivers who fail to pay them bribes at checkpoints," the report said. "Some are killed in the street because, as the police later claim, they are 'armed robbers'; others are killed after arrest, allegedly for attempting to escape. Many disappear in police custody and are likely to have been extrajudicially executed."

Lawyer Vincent E. Obetta said he witnessed one of several police killings detailed in the report by the London-based rights group.

Obetta told the AP that he was on his way to the city of Enugu on May 15 when he reached a police roadblock, where he saw three heavily armed policemen talking to a motorcyclist.

"Next thing, one police inspector pulled his pistol and fired a shot directly into the cyclist," he said.

Obetta then watched as the policeman pressed his gun against the man's bloody chest.

"That's when it dawned on me that the policeman was trying to build a defense as to why the cyclist was killed," he said.