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The man, identified only as 28-year-old Sergei W., hoped to profit from a drop in the Bundesliga football team's share price following last week's attack.

"The accused is suspected of having carried out the attack on the team bus," prosecutors said after the elite GSG 9 police unit arrested the suspect at dawn in Tuebingen, near the southwestern city of Stuttgart.

"He is charged with attempted murder, setting off explosions and causing serious physical injury."

Borussia Dortmund thanked police, who had reportedly been surveilling the suspect for days, following leads including a tipoff from a financial sector source.

Three remotely triggered explosive devices packed with metal pieces went off alongside the team bus on 11 April, minutes after it left the squad's hotel for a Champions League quarter-final match against Monaco. The devices were planted in an adjacent hedge.

The bus windows were shattered by the explosions and Dortmund defender Marc Bartra, 26, suffered a broken wrist. Shrapnel was found as far as 250 metres away.

The suspect was staying in the same hotel as the Borussia Dortmund team and had a view of the scene. He had bought 15,000 so-called put options on the team's shares on the day of the attack, prosecutors said.

These options could have been sold at a pre-determined price by 17 June. A sharp fall in the share price would have guaranteed a high profit.

"A significant drop in the price could have been expected if, as a result of the attack, players had been seriously injured or even killed," prosecutors said.

The suspect took out a load of tens of thousands of euros to pay for the put options, which he bought online while staying at the Hotel L'Arrivee.

In mid-March, he reserved the room for the dates of Borussia Dortmund's scheduled games against Monaco, and hoped to earn up to $4.2 million from the plan, Germany's Bild newspaper reported, with his profit growing the more the club's shares fell.

There is so far no indication of accomplices.

Three purported claims of responsibility stating a radical Islamist motive were found at the scene, on paper bearing no fingerprints, prosecutors said, adding that Islamic studies experts had voiced "considerable doubts" about their authenticity.

Islamic studies experts voiced "considerable doubts" about the letters' authenticity.

An Iraqi man was taken into custody over a suspected Islamist link but was later cleared of involvement in the bus attack.

A purported claim stating a far-right motive sent to German media bore "contradictions and inconsistencies", prosecutors said, adding there was "no indication that it was sent by the perpetrator".