An American woman and her Turkish boyfriend have been arrested by German police on suspicion of planning an attack to mark the anniversary of 11 September.

The 24-year-old man, "who showed a hatred of Americans and Jews", had five pipe bombs and 130kg (290lbs) of explosives in the flat the two shared near the city of Heidelberg, police said.

We suspect that they intended to mount a bomb attack against military installations and the city of Heidelberg

Thomas Schaeuble

The man's 23-year-old fiancee, who is a dual US-German national, worked in a supermarket in one of the many US military installations in the area.

"We have evidence that an attack was planned for 11 September," said Thomas Schaeuble, interior minister for the German state of Baden-Wuerttemberg.

"He seems to be a follower of Osama Bin Laden who is deeply religious and harbours a hatred for Americans and Jews."

He said the woman had also shown a hatred of Jews.

Islamic books

"We suspect that they intended to mount a bomb attack against military installations and the city of Heidelberg,", said Mr Schaeuble.

The man, a strict Muslim who had a picture of al-Qaeda leader Osama Bin Laden at the flat, worked at a chemical warehouse in nearby Karlsruhe.

Islamic literature and a book about building bombs were also found at his residence, said Mr Schaeuble.

"Now we must examine whether he was acting alone or whether there were structures behind this," he said.

The man was being questioned but was not being co-operative, he said.

Sandy Goss, spokesman for US Army Europe which is based on the outskirts of Heidelberg, said he had no details about a possible target.

"All I know is there were two people arrested and we're monitoring the situation closely because we take all these reports seriously," he said.

The BBC's Rob Broomby says the German authorities have been on high alert in the lead-up to the anniversary of the 11 September terror attacks on the US.

Earlier this week, German Interior Minister Otto Schily said he had no information that attacks were being planned in the country.

Germany's war on terror

Germany has played a central role in the investigation into the 11 September attacks, which killed more than 3,000 people.

Three of the hijackers, including suspected ringleader Mohammed Atta, lived in the northern German port city of Hamburg.

In August, German prosecutors also announced they had charged another suspect, Mounir al-Motassadek, with belonging to a terrorist group and being an accessory to murder.

Meanwhile, in the United States the FBI has arrested a 39-year-old German man in New York on suspicion of terrorism.

The German prosecutor's office said the man, from Hamburg, was now being questioned by US officials in Virginia.