Afghan officials say bombs attached to motorcycles have killed four people in separate attacks.

One struck outside a sports stadium in eastern Nangarhar province, killing three on Monday. Akramuddin, a provincial police official, said the explosion occurred as former warlord Gulbuddin Hekmatyar was holding a rally at the stadium in Jalalabad, the province' capital.

Akramuddin, who like many Afghans uses only one name, said the blast took place as the rally ended. Ten people were wounded.

Hekmatyar, previously a declared terrorist by the United States, signed a peace deal with President Ashraf Ghani in 2017 and was removed from the list.

The second motorcycle bomb exploded in western Herat province. Spokesperson Jelani Farhad said one person was killed and seven were wounded.

No groups have taken responsibility for the attacks.