The Times of London reported Ahmed Wali Karzai, the half brother of Afghan President Hamid Karzai, said six people died but a police spokesman said seven foreigners, believed to be British, had been killed. A doctor at a Kandahar hospital said 17 people had been treated for wounds.
The Times said the blast occurred after a vehicle was driven into a compound housing foreigners. The concussion broke windows up to 2 miles away, the newspaper said.
A car bomb hours earlier outside a Kandahar hotel injured eight people, The Times said.
The BBC reported the German soldiers were in an armored vehicle that came under rocket attack during heavy fighting with Taliban militants in Baghlan province. The German Defense Ministry confirmed that in addition to the four German troops killed, five were wounded, the British network said.
A Baghlan provincial police spokesman said three Afghan police officers also died in Thursday's fighting.