Florida Governor Jeb Bush has signed a death warrant for Aileen Wuornos, a prostitute who became one of the first known female serial killers in the United States.

Wuornos volunteered for execution last year and waived all appeals but her death sentence - which is set to be carried out on 9 October - could be delayed by legal wrangles.

Governor Bush is accused of making executions an election issue

She was convicted of shooting six men to death after they picked her up as a hitchhiker on roads around Florida in 1989 and 1990.

Wuornos, now 46, first claimed she had killed all her victims in self-defence after they assaulted her, but later admitted she lied.

Her only motive was robbery and a loathing of men, she said.

Her story has been portrayed in two movies, three books and an opera.

Since 1848, Florida has only executed one woman: Judy Buenoano, who died in the electric chair in March 1998.

'Political move'

Governor Bush - the brother of US President George W Bush - has also ordered the execution of death-row inmate Rigoberto Sanchez Velasco who killed a girl.

Some death-penalty critics accused the governor of making capital punishment a political issue before he goes for re-election in November.

Abe Bonowitz, director of Floridians for Alternatives to the Death Penalty, called the death warrants "a transparent and crass political move at a time when Mr Bush knows that the courts will issue stays in both cases".

In June the US Supreme Court overturned death sentences against dozens of convicted killers in several states.

The ruling in Ring v Arizona forbade judges sentencing prisoners to death without listening to the views of jurors.

We are talking to lawyers and trying to find out if we could sue the state to stop these executions

Abe Bonowitz Anti-death penalty campaigner

But the situation as it referred to Florida was ambiguous and is awaiting clarification in the Florida Supreme Court.

'Election gimmick'

Mr Bonowitz told BBC News Online: "We are talking to lawyers and trying to find out if we could sue the state to stop these executions."

He said he did not expect the executions to take place in October and suspected it was simply an election gimmick by Mr Bush, who faces a tough battle to retain his governorship in November.

He wll be up against a Democrat, either Bill McBride or former US Attorney General Janet Reno.