At least 20 people were killed when a Taliban suicide bomber blew himself up outside a police administration building in Kabul on Monday.
A further 29 people were injured, said Interior Ministry spokesman Sediq Sediqqi said on Twitter.
"The attack was conducted by martyr Mujahid Mohammad from Imam Sahib district, Kunduz province," Taliban spokesman Zabihullah Mujahid said online.
The suicide bomber blew himself up among passers-by at the gate of the headquarters of the National Civil Order Police force, Interior Ministry spokesman Najib Danish said.
"Most of the wounded brought in to Kabul hospitals thus far are men," Health Ministry spokesman Mohammad Ismail Kawusi said.
The Taliban statement claimed that more than 40 police officers were killed or injured.
The attack came as German Interior Minister Thomas de Maiziere was visiting Afghanistan for discussions to include the surge in Afghan asylum seekers reaching Germany last year.