LONDON — Islamic extremists accused of launching failed suicide bomb attacks on London in July 2005 had been under police surveillance months earlier, a court was told yesterday.

If the alleged plot had succeeded, it would have caused carnage on the capital’s transport system for the second time in a fortnight, the court was told.

The coordinated attempt at suicide bomb attacks on three underground trains and a bus, two weeks after the July 7 attacks that claimed 52 lives, failed only because the homemade bomb mixture was not strong enough, it was claimed.

They were not copycat attacks, the jury at Woolwich Crown Court was told, because they had been planned prior to the earlier set of bombings that brought terror to London’s commuters and tourists.

“The ultimate objective was to carry out a number of murderous suicide bombings,” a prosecutor, Nigel Sweeney, told the jury at the high-security Woolwich Crown Court.

One man, Muktar Ibrahim, 28, had actually turned so that the backpack on his back was pointing toward a mother with her child in a pushchair as he tried to detonate the bomb in a tunnel on the Victoria Line causing “panic, fear, and confusion.”