German news weekly Der Spiegel reported on Thursday that it had received materials documenting German surveillance efforts aimed at a number of US businesses and government, including the White House.

The Bundesnachrichtendienst (BND), Germany's foreign intelligence agency, reportedly monitored email addresses at the White House with a list of some 4,000 selector keywords between 1998 and 2006.

Other targets included the US Department of State and Department of Treasury, as well as a number of defense agencies including the US Air Force and the Marine Corps, and the NASA space agency.

Hundreds of foreign embassies as well as international organizations like the International Monetary Fund (IMF) were reportedly not spared from being spied on either, the Spiegel said.

The magazine said it had seen documents showing that the intelligence service, the BND, had a list of some 4,000 so-called selector keywords for surveillance between 1998 and 2006.

Read more: Hans Leyendecker: 'The BND has a life of its own'

Merkel: No spying among friends

The findings will likely prompt further embarrassment for the German government. Berlin reacted furiously when former NSA contractor Edward Snowden revealed documents in 2013 showing widespread US spying, including the tapping of Chancellor Angela Merkel's mobile phone.

Merkel famously said "spying among friends is not on." However, she was forced to swallow those words when it later emerged that the BND had helped US intelligence spy on European allies.

BND making headlines again

While the BND refused to comment on the latest batch of leaked materials, its president, Bruno Kahl, did speak about the organization's future operations and oversight.

"The question concerning who can scout the BND and who cannot does not just depend on increasing authorization for lawmakers, but also implementing an ambitious series of controls," he said.

Unhappy about being spied on, Merkel later had to admit Germany also aided the NSA

The Bundestag, Germany's lower house of parliament, has vowed to rein in the BND, approving a number of new measures and greater oversight over the body.

However, the German government has since been accused of gross negligence in failing to oversee the intelligence agency.

Merkel told a German NSA inquiry committee earlier this year that she knew nothing of the BND's spying activities.

dm/sms (AFP, Der Spiegel)