Two bombs have exploded outside a hotel in western Kabul where Afghan presidential frontrunner Abdullah Abdullah was holding a rally, striking his car and injuring his bodyguards.

Police said two people were killed and 16 wounded in the attack on Mr Abdullah's convoy, the first such incident in Afghanistan's on-going election campaign.

"When I was leaving the rally from the People's Islamic Unity Party, (one of) my car(s) was hit by a roadside bomb and damaged," Abdullah said at another rally soon afterwards.

It was not immediately clear which vehicle Mr Abdullah had been in at the time.

Kabul police spokesman Hashmat Stanekzai confirmed that a suicide bomber detonated the explosives near Abdullah's convoy around noon.

Television images from the location showed at least one dead body on the street, alongside smashed window panes in neighbouring shops and buildings.

The first round of the Afghan elections was praised as an unexpected success after the Taliban failed to cause major trouble, but the security picture looks more challenging ahead of the 14 June run-off.

The Taliban changed its military leadership after the elections, denying that commander Mullah Abdul Qayoum and former Guantanamo Bay detainee had been fired over his failure to prevent large numbers of Afghans from voting in the first round.