A suicide bomber has killed at least 15 NATO troops and Afghan police and civilians, including four U.S. troops, targeting a joint foot patrol by American and Norwegian soldiers, officials said Thursday.

According to eyewitnesses, the suicide bomber detonated his device after steering a motorcycle into the group as they filmed interviews in a street market in Maymana.

A suicide bomber targeted a group of foreign friends near a park in Maymana, the capital of Faryab province, provincial governor Abdul Haq Shafaq told AFP.

The slain U.S. troops had strayed from their base to take photographs in a park, Afghan police said, Reuters reported. Slain soldiers lay on a blood-soaked pavement beside a blown-off leg and strewn helmets. Afghan police rushed to try and move the soldiers into vehicles.

They were military. There are casualties, dead and wounded.

Although there are conflicting reports as to the exact number of dead and injured, Al Jazeera said three foreign soldiers, four Afghan police, an Afghan interpreter, and six civilians were killed in the blast.

The wounded included 30 Afghans and four U.S. soldiers, Al Jazeera added.

Reuters later reported that four U.S. soldiers had been killed in the blast, after straying from their base to take tourist photos.

The news agency described grisly scenes of soldiers laying on a blood-soaked pavement beside a blown-off leg and strewn helmets.

The Taliban has claimed responsibility for the attack.

NATO officials refused to confirm the number of troops killed or injured in the attack, as they tried to determine what had happened.

The latest attack follows a string of similar bombings across the country, raising fears the Taliban is ramping up operations against coalition forces ahead of the annual summer fighting season.

According to local police chief  Abdul Khaliq Aqsai, the attack occurred around 10:30 am local time as American soldiers and Afghan police filmed interviews with local people, asking them about the security situation in Faryab.

A crowd then gathered around the troops, according to the New York Times, and soon after the suicide bomber plowed his motorcycle into the group, detonating the device.

The deaths bring the total number of NATO troops killed in Afghaniatan this year to 100, according to the website http://icasualties.org.