US and NATO commander General Scott Miller was not hurt in the attack inside a heavily fortified government compound in Kandahar city that targeted a high-level security meeting.

But the shooting carried out by a member of the provincial governor's security team killed anti-Taliban strongman and police chief General Abdul Raziq, Afghan and NATO officials said.

"Today I lost a great friend LTG Raziq. We had served together for many years. Afghanistan lost a patriot, my condolences to the people of Afghanistan, " said General Miller in a tweet posted by a NATO-linked account.

"The good he did for Afghanistan and the Afghan people cannot be undone."

Provincial intelligence chief General Abdul Momin Hussainkhail and an Afghan journalist also died in the attack that wounded 13 people, including two Americans and the governor, officials added.

"The attack carried out by a bodyguard of the governor happened moments after the meeting finished, as they were leaving the compound," Afghan Army chief of staff General Mohammad Sharif Yaftali told reporters.

After a meeting chaired by President Ashraf Ghani, "a high-ranking delegation headed by the NDS chief has been deployed to Kandahar to control the situation", Yaftali added.

Afghan security forces swarmed Kandahar city after the shooting that shuttered shops and sent terrified civilians -- already on high alert for violence ahead of Saturday's ballot -- into their homes.

The Taliban said in a Twitter post that Miller and Raziq were the targets of the shooting.

Pentagon spokesman Lieutenant Colonel Kone Faulkner said Raziq or the governor, not Miller, had been the targets.

"Eye witnesses reported that the attacker was focused on Raziq," a US embassy official in Kabul said.

But the unprecedented attack on a US and NATO commander in Afghanistan and the death of Raziq was "a huge blow to stability and to counterinsurgency more broadly", said Michael Kugelman of the Wilson Center.

"The bottom line here is that no one is safe, no matter how powerful they may be and no matter how much security they may expect to receive."

- 'Deep uncertainty' -

The security void left by Raziq's death, who was widely seen as a bulwark against the Taliban insurgency in Kandahar, would create "deep uncertainty" in the south, Johnny Walsh of the United States Insitute of Peace said.

Raziq long controlled the province with an iron hand and was accused of running secret torture chambers, an allegation he denied.

"While General Raziq had long faced accusations of human rights abuses, he was also arguably the most capable military commander in Afghanistan, and widely perceived as the main reason the Taliban have struggled in Kandahar in recent years," Walsh told AFP.

Initial reports indicated Afghan officials were the targets of the attack, NATO's Resolute Support mission spokesman Colonel Knut Peters said, describing it as an "Afghan-on-Afghan" assault.

"We are being told the area is secure."

A hospital official told AFP that several senior officials had been brought to the medical facility, but they would not provide further details.

A witness said the city was "full of military forces".

"They don't allow anyone to come out of their houses," he told AFP.

Afghanistan is tense ahead of the October 20 legislative election after the Taliban pledged to attack the ballot.

More than 2,500 candidates are competing for 249 seats in the lower house.

The election process has already been hit by violence, with hundreds killed or wounded in recent months.

At least 10 candidates have been killed so far including Abdul Jabar Qahraman, who was blown up Wednesday by a bomb placed under his sofa in the southern province of Helmand.

The election is seen as a rehearsal for the presidential vote scheduled for April and an important milestone ahead of a UN meeting in Geneva in November where Afghanistan is under pressure to show progress on "democratic processes" (AFP)