At least 15 people have been injured after a suicide bomber detonated his explosives belt inside a Shia mosque in the eastern Pakistani city of Sargodha.

"The attacker was carrying a bag and detonated the explosives as a guard at the gate tried to stop him," Abdul Ghafoor, a witness who was wounded in the attack, told the Reuters news agency.

People were performing evening prayers at the mosque when the attacker blew himself up.

Sunday's attack appeared to be the latest in a string by Sunni extremists against other Muslims they consider infidels.

Sargodha is in Punjab, Pakistan's most populous province and its political heartland.

The region has increasingly come under attack by al-Qaeda and Taliban, which have logistics and training centres close to the Afghan border several hundred kilometres away.

More than 40 people were killed in twin suicide bombings at a Sufi shrine in the provincial capital Lahore this month.

And more than 80 people were killed in twin attacks in late May on Ahmadis, a religious minority sect declared non-Muslims in Pakistan.