A man accused of conspiring to bomb London's public transport system told a court Monday that he deliberately made fake devices that were not meant to explode but would spread fear and panic in protest against the invasion of Iraq.

Muktar Said Ibrahim, 29, said he learned how to make the devices on the Internet, downloading a Web video on which an Arabic-speaking man in a ski mask described how to make explosives from hydrogen peroxide, an easily obtained household chemical.

"When I saw how easy it is to make the stuff, the idea came to my head that I could use it to make fake explosives," Ibrahim told jurors at London's Woolwich Crown Court.

"Basically, if you know how to make it work, you can make it to not work."

Ibrahim and five other men are being tried on charges of conspiring to bomb the British capital's transport system on July 21, 2005 — two weeks after four homicide bombers killed themselves and 52 bus and subway passengers.

Prosecutors say the July 21 plot failed only because the four bombs, carried onto three subway trains and a bus, failed to explode.

Ibrahim; Yassin Omar, 27; Adel Yahya, 24; Manfu Asiedu, 33; Hussain Osman, 28; and Ramzi Mohamed, 25, all deny conspiring to murder and cause explosions. They each face a maximum sentence of life in prison if convicted.

Ibrahim, the first of the suspects to give evidence, was led to the witness stand by two guards at the high-security court. Dressed in a dark suit and pink tie, he faced the jury and spoke softly as he answered questions from his lawyer, George Carter-Stephenson.

Ibrahim, who was born in Eritrea and moved to Britain at 13, said he was angry about the invasions of Afghanistan and Iraq, and had attended anti-war demonstrations. Finding these had little effect, he said he decided to take "positive action."

"Seeing non-Muslims speaking out and protesting against the war made me think I should do something stronger," he said.

He said he and Omar first discussed the idea of a bomb hoax around September 2004.

"He said, 'What if we do something that would stand out,"' Ibrahim said. "Something like fireworks or firecrackers, something that would make noise and cause panic."

Ibrahim described how he and several of the others bought hydrogen peroxide — a chemical commonly used in bleaching and hair-coloring products — from cosmetics stores, then boiled it in a saucepan at Omar's apartment to reach a concentration of 70 percent. The chemical was mixed with flour, packed into plastic tubs and topped with detonators made with the explosive triacetone triperoxide, or TATP.

The devices were carried onto three subway trains and a bus on July 21.

Ibrahim said his initial plan had been to make eight to 20 realistic-looking devices, which would be left in public places and not detonated.

But after the July 7 bus and subway bombings, the defendants decided instead to mount a series of mock-suicide bombings that echoed the earlier attacks, he said.

"Even though I don't agree with the 7th of July (attacks) it got Britain and the politicians talking about their role in Iraq," he said. "My aim was to cause maximum disruption and maximum publicity and get maximum debate about the war in Iraq.

"I thought this was the right time to put pressure on the government by making a fake suicide mission, but obviously without killing innocent people."

Ibrahim said he thought scientists would soon figure out that the devices were not real.

"I didn't think I was going to be in any trouble, because it was a hoax," he said.