Officials said the suspects had spent time in an al-Qaeda training camp in Pakistan One of the three men held in Germany on Friday on suspicion of planning a bomb attack had received orders from al-Qaeda, prosecutors have said.
A senior al-Qaeda figure on the Afghanistan-Pakistan border gave the order last year. Prosecutors said the target had not yet been chosen.
The three suspects were arrested in the cities of Duesseldorf and Bochum after allegedly buying bomb-making chemicals.
They had been under surveillance for several months.
Deputy federal prosecutor Rainer Griesbaum named the three suspects as Abdeladim K, a 29-year-old from Morocco; Jamil S, a 31-year-old German-Moroccan; and Amid C, a 19-year-old German-Iranian.
He said Abdeladim K had been in regular contact with a senior al-Qaeda member who was on the Afghan-Pakistan border.
Mr Griesbaum said the trio had planned to set off a shrapnel-laden bomb in a crowd, but the plot was “still in the experimental phase”.
Joerg Ziercke, president of the Federal Office of Criminal Investigation (BKA), said there had been seven or eight people in the cell.
He said the group’s ringleader, Abdeladim K, had been in the country illegally since November last year.
Mr Griesbaum said he had spent time in an al-Qaeda training camp in the Pakistani tribal region of Waziristan, close to the Afghan border.
Der Spiegel reported that the German secret service was aided by the CIA and Moroccan authorities in a three-month operation.
German intelligence intercepted phone calls and e-mails from one of the suspects.
They were arrested when investigators heard the three were planning a test after buying chemicals which could be used to make a bomb, police said.
Islamists in Germany have been associated with several attacks.
9/11 ring-leader Mohammed Atta had worshipped in a mosque in Hamburg.
So far, though, there has been no big attack in Germany itself.
In 2006 homemade bombs were placed on trains in Cologne but failed to explode.
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