German Chancellor Angela Merkel, reportedly the target of U.S. snooping on her mobile phone, said Thursday that such conduct between friends was unacceptable.

"Spying between friends, that's just not done," Merkel said as she arrived for a two-day European Union summit where the growing spy scandal has hijacked the agenda.

Germany on Thursday summoned the U.S. ambassador to Berlin over suspicions that Washington spied on Chancellor Angela Merkel's mobile phone, a foreign ministry spokeswoman said.

Foreign Minister Guido Westerwelle will personally meet with U.S.. envoy John B. Emerson later Thursday, the spokeswoman told AFP, in a highly unusual step between the decades-long allies.

President Barack Obama has assured German Chancellor Angela Merkel the United States is not monitoring her communications, but the White House did not deny reports U.S. spies eavesdropped on her cellphone in the past.

"The President assured the Chancellor the United States is not monitoring and will not monitor the communications of the Chancellor," White House spokesman Jay Carney said Wednesday.

Germany said Wednesday its robust economy would fuel record employment this year and next as well as boost consumer spending and industrial investment.

The economy ministry said in its autumn forecast that gross domestic product would expand 0.5 percent this year and 1.7 percent next year, confirming reports from sources on Tuesday and underlining the rude health of Europe's top economic power.

European Union ministers urged Yemen Monday to deliver in a probe into the October 6 killing of a security official at Germany's embassy in Sanaa.

Worried by a surge in attacks and kidnappings rendering security "fragile" across the country, the ministers called on the Yemeni authorities "to do their utmost to investigate".

Top members of Germany's Social Democratic Party agreed Sunday to launch coalition talks with Chancellor Angela Merkel as she attempts to form a government for Europe's top economy.

An overwhelming majority of the 200 or so SPD members backed their leaders' recommendations to open formal coalition talks with Merkel following a hefty defeat for the party in September 22 elections.

Germany's foreign ministry said Thursday that its embassy in Afghanistan was shut but declined to comment on a media report it had been closed in response to a security threat.

"It is correct that the German embassy in Kabul is currently closed," a foreign ministry spokesman told Agence France Presse, confirming a report in the Die Welt daily.

German Chancellor Angela Merkel's conservatives and her defeated election rivals the center-left Social Democrats agreed Thursday to launch formal talks to build a "grand coalition" government.

Such a left-right alliance ruling Europe's biggest economy would have a strong parliamentary majority and be able to drive through policy against the opposition of the two smaller parties, the ecologist Greens and the far-left Linke.

The White House Wednesday said Iran had shown a new level of "seriousness and substance," at talks with world powers on its nuclear program which just wrapped up in Geneva.

President Barack Obama has called on Tehran to show it is serious about substantive nuclear discussions following a diplomatic opening pioneered by the new government of President Hassan Rouhani.

German Chancellor Angela Merkel voiced concern Wednesday to Russian President Vladimir Putin over the detention of 30 Greenpeace members who had protested Arctic drilling.

The environmental activists have been held on piracy charges in the northern region of Murmansk for almost three weeks after their ship Arctic Sunrise was seized by Russian security forces in a commando-style operation.