An Afghan official says a bomb attached to a motorcycle exploded outside a sports stadium in eastern Nangarhar province's capital, killing three people.

Also on Monday, another motorcycle bomb exploded, this one in western Herat province. Spokesman Jelani Farhad says one person was killed and seven were wounded.

Akramuddin, a police official in Nangarhar, says 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, says 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.

No group has taken responsibility for the attacks.