President Hamid Karzai said on Saturday that Afghanistan and the United States are engaged in peace talks with the Taliban, even as insurgents stormed a police station near the presidential palace, killing nine people.

The brazen attack in the heart of Kabul's government district provided a sharp counterpoint to Karzai's first official confirmation that the US and Afghan governments are holding discussions with the Taliban.

The Obama administration neither directly confirmed nor denied Karzai's statement.

State Department spokesman Mark Toner said the US has ‘consistently supported an Afghan-led’ peace process.

"Over the past two years, we have laid out our red lines for the Taliban: They must renounce violence; they must abandon their alliance with al-Qaida; and they must abide by the constitution of Afghanistan," Toner said. "This is the price for reaching a political resolution and bringing an end to the military actions that are targeting their leadership and decimating their ranks."

Saturday's violence underscored the challenges facing any possible negotiated settlement to the decade-long war.

Three men dressed in Afghan army uniforms stormed the police station near the presidential palace and opened fire on officers, said Mohammed Honayon, a witness. The Interior Ministry said in a statement that one of the attackers detonated a suicide bomb vest outside the gates while the others rushed in and began shooting.

The crackle of gunfire echoed through the streets typically bustling with shoppers and government employees on a Saturday, the start of Afghanistan's work week. The fighting ended by 3pm when security forces shot dead the two other attackers. Three police officers, one intelligence agent and five civilians were killed in the attack, the Interior Ministry said.

Taliban spokesman Zabiullah Mujahid claimed responsibility for the attack in a text message (to the news agency), saying the group dispatched three suicide bombers.

The assault occurred shortly after Karzai announced during a speech at the presidential palace that his government and the US have begun preliminary negotiations with the Taliban aimed at ending the conflict.

"In the course of this year, there have been peace talks with the Taliban and our own countrymen," Karzai said. "Peace talks have started with them already and it is going well. Foreign militaries, especially the United States of America, are going ahead with these negotiations."

Karzai said some of the Taliban emissaries that have met with members of the peace council he set up were only representing themselves, while others were speaking for the broader movement. The exact nature of the contacts was not immediately clear, and Karzai said that no government official outside of the council had contact with them.

"The peace council is trying to get connected to them to bring peace," the president said.

Attacks in the Afghan capital have been relatively rare, although violence has increased since the May 2 killing of Osama bin Laden in a US raid in Pakistan and the start of the Taliban's annual spring offensive.

The capital is one of seven regions scheduled to be handed over to Afghan security control in late July — part of NATO's efforts to begin transferring security responsibilities ahead of its planned 2014 withdrawal from the country. The US also plans to start drawing down troops in July.

The last major attack in Kabul took place last month when a suicide bomber wearing an Afghan police uniform infiltrated the main Afghan military hospital in late May, killing six medical students. A month before that, a suicide attacker in an army uniform sneaked past security at the Afghan Defence Ministry, killing three.

Insurgents also attacked three convoys ferrying fuel and supplies to NATO troops stationed in western and eastern Afghanistan, killing nine Afghan security guards and torching at least 15 fuel tankers, officials said.

Two of the supply convoys hit roadside bombs Saturday in eastern Ghazni province, killing four Afghan security guards escorting the trucks to a nearby base for Polish troops, said provincial police chief Mohammed Hussain.

Insurgents also ambushed a NATO fuel convoy late Friday along the border between Herat and Farah provinces in the west, killing five Afghan guards and wounding seven others before setting fire to the tankers, said Abdul Rashied, a local police chief.

In the eastern city of Jalalabad, insurgents kidnapped a provincial council member for Logar province and three of his family members.

Two NATO service members also were killed Saturday in an insurgent attack in southern Afghanistan, according to the alliance. At least 32 international soldiers have died in Afghanistan so far this month, raising the death toll for 2011 to 238.