By Crispin Thorold
BBC correspondent in Kabul
The killing of Bettina Goislard, in the centre of Ghazni on Sunday, has sent shock waves through the international community in Afghanistan.
Some fear aid agencies may pull out if attacks continue
The twenty-nine year-old Frenchwoman had been working in the city since June 2002.
Colleagues from the United Nations refugee agency say she was well known to, and well liked by, locals.
The shooting near the city's bazaar, in the middle of the day, is the latest in a string of attacks against humanitarian workers in Afghanistan.
Twenty-six Afghan staff and two foreigners have been killed since March.
This is, however, the first murder in an urban centre.
A "deeply worrying development", says one aid worker in the capital, Kabul.
"If it can happen in Ghazni, it can happen anywhere."
There have been other indications that the modus operandi of the militants is changing, following, some warn, the "example" from Iraq.
There have been two bombings in Afghanistan in as many weeks, one in Kabul, the other in the southern city of Kandahar.
There were no fatalities, but both targeted the international community.
President Hamid Karzai has warned Afghans to be prepared for further terrorist attacks in the run-up to December's loya jirga - the tribal gathering which will debate and finalise Afghanistan's draft constitution.
Analysts believe it's too early to link the apparent upsurge in violence with any particular event, but it's clear that the remnants of the Taleban are becoming ever bolder.
Ms Goislard (left): Shot in her car at point-blank range
Diplomats say that the militants fighting against the US-led coalition consider aid workers and all Westerners in Afghanistan "legitimate targets".
In response, the United Nations is urgently reviewing it's already stringent security arrangements.
Other organisations are also trying to keep their staff safe without, if possible, jeopardising projects.
All agree that safety must, of course, come first, but there's also a fear that if the attacks continue, a further reduction of aid work is inevitable.
Recently ACBAR, an umbrella body for agencies in Afghanistan, cautioned that the "security situation is forcing humanitarian organisations to restrict aid and development, resulting in a growth in public support for radical movements".
To break that vicious cycle, aid workers have been calling for months for an expansion of the Nato-led international peacekeeping force, Isaf.
The United Nations Security Council recently gave Nato the go-ahead for patrols outside the capital.
But progress has been slow.
The German army is deploying to the relatively safe northern city, Kunduz, but large swathes of the country remain lawless.
Militias nominally loyal to the Afghan Government attempt to keep the peace, but numerous districts are no-go areas.
The senseless killing of Bettina Goislard is yet another reminder of the dangers humanitarian workers now face every day in Afghanistan.
Privately some agencies warn that if the attacks continue, they will have to pull out.
That would leave one of the world's poorest countries to fend for itself once again.