KABUL (Reuters) - A suicide car bomber killed 13 American troops and civilian employees of the NATO-led force in the Afghan capital Kabul Saturday, the deadliest single ground attack against the coalition in 10 years of war in Afghanistan.

"Five International Security Assistance Force (ISAF) service members and eight ISAF civilian employees died following a suicide vehicle-born improvised explosive device attack in Kabul earlier today," ISAF said in a statement.

A Pentagon spokesman said all 13 of the ISAF fatalities were American.

Three other civilians and a police officer were also killed in the attack on a convoy of military vehicles, a spokesman for the Afghan interior ministry said.

Excluding aircraft crashes, it was the deadliest single incident for the coalition since the war began in 2001.

Lethal attacks are relatively rare in heavily guarded Kabul, compared with the south and east of Afghanistan, but Saturday's killings came less than two months after insurgents launched a 20-hour assault on the U.S. embassy in the capital.

The assault on the ISAF convoy took place late in the morning in the Darulaman area in the west of the city, near the national museum.

The former royal palace, now in ruins, is also in the area, along with several government departments, and Afghan and foreign military bases.

The Taliban later claimed responsibility for the attack, saying they packed a four-wheel-drive vehicle with 700 kg of explosives.

SECURITY HANDOVER

The attack is likely to heighten worries about the reach of insurgent forces as the United States and its allies prepare to hand over responsibility for security to Afghan forces by 2014.

"We are confident we can undertake the transition," NATO's senior civilian representative in Afghanistan, Simon Gass, said at a meeting in Kabul Saturday before the attack. "If we compare the security situation to how it was two years ago, we can see very dramatic improvements in many areas."

In two other attacks Saturday, three Australians and an Afghan linguist were killed in Uruzgan province in southern Afghanistan when an attacker wearing an Afghan National Army uniform opened fire on them, authorities in neighboring Kandahar province said.

In Kunar province, east of Kabul, a teen female suicide bomber killed herself and wounded several National Directorate of Security (NDS) members in an attack on the NDS building.

ISAF commander General John Allen condemned the attacks in a statement later Saturday, as did the U.S. embassy in Kabul.

"Our common enemy continues to employ suicide attackers to kill innocent Afghan fathers, mothers, sons and daughters, as well as the Coalition forces who have volunteered to protect them," Allen said in a statement.

Violence across Afghanistan is at its worst since the start of the war 10 years ago, according to the United Nations, despite the presence of more than 130,000 foreign troops.

ISAF says there has recently been a fall in attacks by insurgents but this data excludes attacks that kill only civilians and attacks on Afghan security forces operating without international troops.

Thursday, insurgents armed with rifles and rocket-propelled grenades attacked two bases used by foreign troops in southern Afghanistan. An Afghan interpreter working for ISAF was killed in that attack, which stretched into Friday before the last of the four insurgents were killed.

There has been a series of high-profile assassinations, as well as day-to-day attacks by Taliban raiders, over the past year.

More than a dozen people were killed in the September attack on the U.S. embassy and ISAF headquarters.

(Reporting By Christine Kearney; Writing and additional reporting by Daniel Magnowski)