German spy chiefs will travel to the US next week to demand answers following allegations that US intelligence has been tapping Chancellor Angela Merkel's mobile phone, as a row over US snooping threatened to hurt transatlantic ties.
Documents leaked by former US intelligence contractor Edward Snowden showing sweeping US surveillance on ordinary citizens' internet searches and telephone records have already sparked outrage worldwide.
But the furore has intensified after allegations that world leaders including the presidents of Brazil and Mexico have been among spying targets.
This week, the scandal widened to Europe, with allegations that Merkel's phone was being tapped, prompting Berlin to summon the US ambassador - a highly unusual move between the close allies.
"High-ranking government representatives will go rapidly to the United States in order to push forward discussions with the White House and the NSA (National Security Agency) on the allegations raised recently," Georg Streiter, the chancellor's deputy spokesman, said Friday.
German media quoting sources close to the intelligence service reported on Saturday that the delegation will include top officials from the German secret service.
Meanwhile, several thousand protesters gathered in Washington to call for new US legislation to curb the NSA's activities and improve privacy.
"It's not just Americans being caught in this dragnet. We need to stand up for the rest of the world too," Free Press media and technology advocacy group president and chief executive Craig Aaron told the crowd, which brandished banners reading "Stop watching us".
Merkel telephoned US President Barack Obama on Wednesday saying that spying on allies would be a "breach of trust" between international partners.
"Spying between friends, that's just not done," Merkel said, as she was heading into a EU summit earlier this week.
In the latest Snowden revelations, German weekly Der Spiegel reported late on Saturday that leaked NSA documents showed Merkel's phone has appeared on a list of spying targets since 2002, and was still under surveillance several weeks before Obama visited Berlin in June.
The spying row has prompted European leaders to demand a new deal with Washington on intelligence gathering that would maintain an essential alliance while keeping the fight against terrorism on track.
The 28 leaders also warned at this week's summit that while the bloc and the United States share a "close relationship", it must "be based on respect and trust".
Germany and Brazil are also working on a UN General Assembly resolution to highlight international anger at US data snooping in other countries, diplomats said.
