A photo taken in June 2013 shows US President Barack Obama and German Chancellor Angela Merkel gesturing during a news conference at the Chancellery in Berlin. German Chancellor Angela Merkel said on Saturday that she regrets the deterioration of the trust between the US and Germany, amid a row with the US over spying. [Photo/AFP]

WASHINGTON - US President Barack Obama and German Chancellor Angela Merkel on Wednesday reaffirmed the necessity of close US-German counterterrorism and broader security cooperation.

In a telephone talk, Obama expressed condolences over the attacks in southern Germany, the White House said, adding that the US government offered its full support to Germany as the investigations into the recent violent attacks proceeded.

Germany was shocked by four violent attacks within last week in the southern part of the country.

On Sunday, a 27-year-old Syrian blew himself up and wounded 15 people outside a music festival in Ansbach, a city in the state of Bavaria.

It happened just hours after a 21-year-old Syrian refugee killed a pregnant Polish woman and injured two people with a machete in Reutlingen, a city in Baden-Wuerttemberg.

Over the phone, Obama and Merkel also discussed the situation in Ukraine and reiterated the urgent importance of durably ending the violence in eastern Ukraine by rapid implementing the Minsk agreements.