President Obama this evening spoke with Russian President Putin, the White House announced. It was not clear from the White House statement who initiated the call.
From the statement:
President Obama spoke by phone tonight with President Putin of Russia. President Putin expressed his condolences on behalf of the Russian people for the tragic loss of life in Boston. President Obama thanked President Putin for those sentiments, and praised the close cooperation that the United States has received from Russia on counter-terrorism, including in the wake of the Boston attack. The two leaders agreed to continue our cooperation on counter-terrorism and security issues going forward.
The two brothers alleged to have committed the Boston Marathon attack are Muslims originally from the Caucasus region of Russia, where terrorists who have launched attacks in Russia are based. The United States will presumably seek the assistance of Russia in investigating the background of the terrorists and the identities of terrorists within Russia who may have planned and directed the attacks.