Insurgent attack across Afghanistan killed seven American soldiers and at least two Afghan civilians Monday, as thousands of U.S. Marines continue their offensive against the Taliban in southern Helmand province.

A U.S. military spokesman, Chief Petty Officer Brian Naranjo, said four U.S. soldiers died when their vehicle struck a roadside bomb outside the northern city of Kunduz.

The Taliban claimed responsibility for the attack.

The U.S. military spokesman said an explosion in the south killed two more U.S. troops, while another American soldier died of wounds sustained during a firefight Monday with militants in eastern Paktia province.

In southern Kandahar province, local officials said a suicide bomber detonated his explosives-laden car near the entrance of the regional NATO military base, killing two Afghan civilians and wounding 14 others.

In other developments, Russia has agreed to let the United States fly troops and weapons across its territory to Afghanistan.

The deal follows talks in Moscow between U.S. President Barack Obama and his Russian counterpart, Dmitri Medvedev.

Under the agreement, Russia will allow 4,500 U.S. military flights annually -- or about 12 each day -- over Russian territory.

Some information for this report was provided by AFP, AP and Reuters.