Radio messages intercepted by Germany show government forces had asked Assad for approval to use chemical weapons on multiple occasions in past months, but permission had always been denied. Stephan Jansen/AFP/Getty Images

Syrian government forces may have carried out a chemical weapons attack close to Damascus without the personal permission of President Bashar al-Assad, Germany's Bild am Sonntag paper reported on Sunday, citing German intelligence.

Syrian brigade and division commanders had been asking the Presidential Palace to allow them to use chemical weapons for the last four-and-a-half months, according to radio messages intercepted by German spies, but permission had always been denied, the paper said.

This could mean Assad may not have personally approved the attack close to Damascus on Aug. 21 in which more than 1,400 are estimated to have been killed, intelligence officers suggested.

Germany's foreign intelligence agency (BND) could not be reached for comment.

Bild said the radio traffic was intercepted by a German naval reconnaissance vessel, the Oker, sailing close to the Syrian coast.

Last week the head of the BND, Gerhard Schindler, gave confidential briefings to the German parliament's defense and foreign affairs committees. Bild said Schindler told the defense committee that Syria's civil war could continue for years.

The chief of staff of Germany's armed forces, General Volker Wieker, also told lawmakers the influence of al-Qaeda-linked forces within the rebels was becoming stronger and stronger.