The three top officials in Afghanistan's Kandahar province were killed when their own guards opened fire on them at a security conference on Thursday, the deputy provincial governor said, however, a Taliban spokesman said the target was Washington's top general in Afghanistan, General Scott Miller, who escaped without injury, according to Nato.

Kandahar's deputy provincial governor Agha Lala Dastageri said powerful provincial police chief Abdul Razik and the province's intelligence chief Abdul Mohmin died immediately in the attack, while provincial governor Zalmay Wesa died later of his injuries at a hospital.

A Taliban spokesman who claimed responsibility for the attack told The Associated Press that US Gen Scott Miller, commander of US and Nato troops in Afghanistan, was the target. Nato officials say Miller escaped unharmed.

Taliban spokesman Qari Yousuf Ahmadi took responsibility for the attack. He too said all three officials were killed.

The security meeting inside the sprawling provincial governor's residence was being held ahead of Saturday's parliamentary elections.

Razik was a particularly powerful figure in southern Kandahar and a close US ally despite widespread allegations of corruption. He ruled in Kandahar, the former Taliban heartland, with an iron fist and had survived several attempts to kill him, including one last year that resulted in the death of five diplomats from the United Arab Emirates.

Security has been steadily deteriorating in Afghanistan with increasingly brazen attacks being carried out by insurgents and Afghanistan's security forces have been on high alert ahead of Saturday's elections.

The Taliban have threatened the polls and warned teachers and students not to participate in the vote and not to allow schools to be used as polling centres. The insurgents said in a statement on Wednesday that they will target Saturday's elections, which they view as illegitimate, but that they do not want to harm civilians.

Peace in Afghanistan vital for regional peace, says PM Khan

The Pakistan government has condemned the brazen attack, saying "for the continuation of the democratic process in Afghanistan it was necessary for peace to prevail in the country".

Prime Minister Imran Khan expressed condolences to President Ghani, the families of the victims and the people of Afghanistan recognising that "peace and security of Pakistan is inextricably linked to peace and security in Afghanistan".

Moreover, military spokesperson Maj Gen Asif Ghafoor tweeted a statement of condemnation on behalf of Army Chief Gen Qamar Bajwa which expressed a desire to see security forces bring an end to "this prolonged violence in Afghanistan".

The army chief assured support in all initiatives towards that end.