Six men plotted to kill London transport passengers with bombs made from hydrogen peroxide and flour just two weeks after suicide attackers killed 52 commuters, a British prosecutor told a jury Monday.

No one was killed in the attempted bombings on July 21, 2005, because the devices failed to explode. Forensic scientists had tested the mixture, however, and "in every experiment this mixture has exploded," prosecutor Nigel Sweeney said.

"This case is concerned with an extremist Muslim plot, the ultimate objective of which was to carry out a number of murders and suicide bombings," Sweeney told jurors.

Ibrahim Muktar Said, 28, Ramzi Mohamed, 25, Yassin Omar, 26, Manfu Asiedu, 33, Adel Yahya, 24, and Hussain Osman, 28 — all from London — deny charges of conspiracy to murder and conspiracy to cause explosions.

The apparent bid to bomb three London Underground trains and a bus shook a city reeling from the July 7 explosions that killed 52 passengers and four bombers — the deadliest attack on London since World War II and the first suicide bombings in Western Europe.

On July 21, devices were triggered, again on three subway trains and a double-decker bus. They failed to detonate fully, and no one was injured.

Click here to go to FOXNews.com's Europe Center.

Most of the suspects were arrested in Britain a few days after the failed bombings. Osman fled to Italy, and was detained in Rome a week after the attacks.

Eleven other people — including Osman's wife and sister-in-law — have been charged with assisting the accused or failing to disclose information. Their trials are due to take place later this year.

The case is being heard by judge Adrian Fulford at Woolwich Crown Court, a heavily fortified courthouse next to London's high-security Belmarsh Prison. It is expected to last between three and four months.

During jury selection last week, the judge told prospective jurors the trial "comes after all the shock, confusion and press reporting" of attacks in July 2005, "most particularly the death and the injuries of those who were involved in the incidents on July 7."

He said they would be asked to decide whether the defendants intended to kill or injure others.

"It is not about whether killing or causing serious injury to people is justified on the basis of any ideology or belief," he said.

Visit FOXNews.com's War on Terror Center for complete coverage.