A suicide bomber has struck an election rally in Afghanistan’s eastern Nangarhar province, killing at least 13 people and wounding more than 30, a provincial official said.

The attack, the first since campaigning began last week ahead of the elections for the lower house of parliament, underscored the widespread violence gripping the country 17 years after the US-led invasion toppled the Taliban.

The vote is scheduled for October 20 but it is unclear if the balloting will go ahead in areas controlled by the Taliban.

Tuesday’s attack took place in Nangarhar’s district of Kama as supporters of Abdul Naser Mohmand gathered in the afternoon to back his campaign as an independent candidate in the elections.

According to Attahullah Khogyani, spokesman for the provincial governor, some of the wounded were in a critical condition, which added to concerns the death toll could rise further.

No group immediately claimed responsibility for the attack but both the resurgent Taliban and Afghanistan’s Islamic State affiliate are active in Nangarhar.

“Most of the people killed or wounded are elders who had gathered for the campaign rally,” said Mr Khogyani.

The election campaign kicked off last Friday with 2,565 candidates vying for a seat in the 249-member chamber, including 417 women candidates.

In the run-up to campaigning, five candidates were killed in separate attacks, including two in Kabul and one each in Nangarhar, southern Kandahar and northern Parwan province.

Officials from the country’s Independent Election Commission said two candidates were abducted and their fates remain unknown while three others were wounded in attacks.

Separately, Afghan security forces killed three bodyguards of an independent parliamentary candidate during a raid on a house near his residence in the eastern Kunar province on Sunday.

But the security challenges are not the only worries ahead of the elections.

A number of political parties and opposition groups have expressed concerns over the transparency of the vote, leading to demands that a biometrics system be used to register voters – a first in Afghanistan’s history.

In Afghanistan, the parliament includes both a lower and an upper house, but only members of the lower house are directly elected.

The upper house consists of a mixture of parliamentarians chosen from local councils and those appointed by the president, as well as members elected in district elections.