A suicide attack on a political rally in eastern Afghanistan killed at least 13 people yesterday, officials said, as the country braces for an escalation in violence ahead of this month's parliamentary election.

The attack is the first suicide assault since campaigning officially began last Friday for the long-delayed ballot, preparations for which have already been marred by dozens of bloody attacks.

More than 40 people were wounded, some of them critically, when the militant blew himself up among supporters of candidate Abdul Nasir Mohmmand in Nangarhar province, provincial governor spokesman Ataullah Khogyani said.

Mohmmand survived the attack, Khogyani confirmed, but he did not say if the candidate had been hurt.

Provincial health director Najibullah Kamawal put the death toll slightly higher at 14.

An AFP reporter saw numerous ambulances delivering bodies and wounded people to a hospital in the provincial capital of Jalalabad.

Sayed Humayun, who had brought his injured cousin to the medical facility, said scores of people had been inside a hall listening to campaign speeches when the bomber struck.

"I heard a big explosion," Humayun told AFP.

"For a while I could not see, I thought I was blinded, but later I saw I was surrounded by bodies and people covered in blood."

The force of the blast caused the ceiling to collapse on top of the gathering. "There are still people trapped under the rubble," Malik Zeerak, who was at the rally, told AFP.

No group immediately claimed the attack, but the Islamic State group has taken responsibility for most of the suicide bombings in recent months.