KANDAHAR, Afghanistan: An 18-year-old woman working for the Afghan government was killed in Kandahar on Tuesday; hours after suicide bombers targeted a nearby Nato fuel depot, killing four security guards.

Rabia Sadat, who worked on rural development, was shot dead as she left home in the southern city of Kandahar to go to work at around 8:00 am (0330 GMT), provincial spokesman Zalmai Ayoubi said.

She had been assigned to a Western-funded project which aims to boost the quality of life in Afghanistan's deprived villages by improving irrigation and the provision of drinking water.

The Taliban did not immediately claim responsibility for the attack. But they have frequently targeted government employees in a 10-year insurgency against US-led foreign forces and President Hamid Karzai's Western-backed government.

Kandahar is the largest city in southern Afghanistan, the Taliban's birthplace and traditional heart of the insurgency.

In recent weeks, the city's mayor and Karzai's powerful brother, Ahmed Wali Karzai, have both been assassinated in Kandahar.

The attacks have raised fears about a power vacuum in the south as Nato troops start withdrawing from Afghanistan under a tight timetable set to repatriate all foreign combat troops by the end of 2014.

The government blamed Tuesday's killing on “enemies of Afghanistan”, a phrase often used by officials to refer to insurgents.

Before being ousted from power by the 2001 US-led invasion, the Taliban banned women from attending school or working outside the home under their interpretation of Islamic law.

Near the city, three suicide bombers struck at a fuel depot for foreign forces, killing four security guards late Monday.

The facility belongs to logistics company Supreme and is near the sprawling Kandahar airfield where thousands of foreign troops are based and which acts as a hub for operations across south Afghanistan.

The police commander for southern Afghanistan, General Salem Ihsas, said four Afghan guards working for a private security firm were killed in the assault at around 9:00 pm.

He said eight other guards - three from Nepal and five from Afghanistan - were wounded when two suicide bombers blew themselves up at the compound gates.

A third was shot dead in an ensuing gun battle.

Taliban spokesman Qari Yousuf Ahmadi said the militant group was behind the attack in a telephone call from an undisclosed location.

The insurgents frequently target both foreign and Afghan organisations which work with the 140,000-strong foreign military in Afghanistan as well as fuel convoys and tankers supplying the international force.

Nato's US-led International Security Assistance Force relies on contractors to provide a wide range of services in Afghanistan, particularly at large hub bases such as Kandahar airfield.

Supreme's website says it provides services to foreign military including fuel, catering, cargo transportation and logistics.

It adds that it has over 50 years' experience working in “demanding environments”.

The company, which is headquartered in Amsterdam, was not immediately reachable for comment.