German Chancellor Angela Merkel said Monday that allegations of spying by a suspected U.S. double agent are serious, after ministers in her government called for a swift response from Washington.

Merkel made the remarks in a joint press conference with Chinese Premier Li Keqiang at Beijing's Great Hall of the People, on her seventh visit to China since taking office in 2005.

German Chancellor Angela Merkel arrived in China on Sunday for her seventh visit since 2005, with economic ties topping the agenda and a high-powered business delegation in tow.

Merkel touched down early Sunday in the southwestern city of Chengdu, where she met local officials, visited a market and toured a factory operated by German car manufacturer Volkswagen.

German ministers on Sunday called for a swift response from the U.S. to allegations of spying by a suspected double agent, which have raised fears of fresh tensions between the two allies.

"I expect now for everyone to assist in the speedy clarification of the accusations, and quick and clear statements, also by the U.S.," Interior Minister Thomas de Maiziere told Bild newspaper in comments released ahead of Monday's edition.

Mats Hummels headed Germany to a 1-0 victory over old rivals France on Friday, and took his country to the World Cup semi-finals for a record fourth straight time.

The center-back's powerful 13th-minute header decided the nervy encounter between two sides who have traditionally produced sensation matches. 

German authorities have arrested a suspected double-agent accused of spying for the U.S. on a parliamentary panel investigating NSA surveillance, media reports said Friday.

The suspect is an employee of Germany's foreign intelligence service who was passing information to U.S. spies, said the reports, which threaten to undermine efforts to repair U.S.-German ties after last year's shock revelations of widespread U.S. snooping.

Germany has adopted a new law that allows dual citizenship for the children of immigrants, a step that will benefit mainly young people from the country's three-million-strong Turkish-origin community.

Until now, Germany-born children of immigrants from most non-EU countries were granted both German and their parents' citizenship at birth but then had to opt for one of them by age 23.

Russian President Vladimir Putin on Thursday expressed "deep concern" over the growing number of civilian casualties and refugees in eastern Ukraine.

"Vladimir Putin expressed deep concern over the growing number of peaceful civilians and a sharp increase in the number of refugees from southeastern Ukraine in Russia," the Kremlin said in a statement after a telephone conversation between Putin, German Chancellor Angela Merkel and French President Francois Hollande.

France said Tuesday there would be no let-up in diplomatic efforts to bring peace to Ukraine as the Kiev government announced the end of a ceasefire in the restive east of the country.

France and Germany led efforts overnight to "de-escalate" the conflict with talks held between the foreign ministers of both countries and their counterparts in Russia and Ukraine, French Foreign Minister Laurent Fabius said.

German pastor Christian Fuehrer, a pro-democracy leader in the former East Germany, died Monday at the age of 71, a quarter century after the fall of the Berlin Wall.

The Lutheran leader had launched the weekly "prayer for peace" which swelled into the massive "Monday demonstrations" that ushered in the non-violent overthrow of the communist regime.

Russian President Vladimir Putin on Monday called for Ukraine's truce to be extended and for new talks between Kiev and separatists, just hours before the current ceasefire expires.

"Vladimir Putin stressed the importance of extending a ceasefire as well as creating a reliable mechanism to control the observance of the truce with an active role of the OSCE," the Kremlin said in a statement after Putin held talks with his French counterpart Francois Hollande, Germany's Angela Merkel and Ukrainian President Petro Poroshenko.