A suicide attack on a government bus in Kabul on Sunday killed three people and wounded 18, the second attack on employees of the Afghan Attorney General's office in a week, an official said.

The spokesman for the Interior Ministry, Sediq Sediqqi, said that the dead and wounded included both government workers and civilians.

The attack happened during the afternoon peak hour, when the bus was taking workers home. He said it was carried out by "a suicide bomber on foot."

The incident comes a week after a similar early morning attack on a bus from the same office in which one person was confirmed dead.

The Taliban claimed responsibility for the attack in a tweet on the militant group spokesman's verified Twitter account.

Earlier Sunday, four intelligence agency employees were wounded in an attack at the agency's office in the southern city of Kandahar.

Hasib Sediqi, spokesman for the National Directorate for Security, said a suicide truck bomber detonated his explosives near the agency's compound. The Taliban claimed responsibility for that attack, as well as another attack in northwestern Badghis province in which insurgents attacked government offices in the Jawand district.

Mirwais Mirzakwal, a spokesman for the provincial governor there, said Taliban gunmen were dug in near the district's main bazaar.

The insurgents, who have been fighting to overthrow the Kabul government for more than a decade, launched their annual warm weather offensive on April 24 with a complex operation in the northern city of Kunduz.

More than 100,000 people have been displaced by the fighting. The provincial governor Mohammad Omer Safi said "foreign fighters" possibly aligned to the Islamic State group had been fighting alongside Taliban gunmen.