German spies are stationed off the Syrian coast and are passing on information designed to help rebels in their fight against President Bashar al-Assad, a newspaper reported on Sunday.

Agents from Germany's foreign intelligence service (BND) are operating on ships off the coast with technology allowing them to observe troop movements 600 kilometres (400 miles) inside the country, said the Bild am Sonntag weekly.

They pass their findings onto US and British officers who then supply the rebels with the information, Bild said.

The paper quoted an unnamed US official as saying that "no Western intelligence service has such good sources inside Syria" as Germany's BND.

German agents are also active in the Syrian conflict from the NATO base in the Turkish city of Adana, according to Bild.

"We can be proud of the significant contribution we are making to the fall of the Assad regime," a BND official told Bild.

The BND was not immediately available for comment.

Berlin insists military intervention is not the way to solve the conflict but Defence Minister Thomas de Maiziere said earlier this month that Germany must help in other ways, providing humanitarian aid and logistical support.