Afghan policeman shoots dead AP reporter Niedringhaus

Two female journalists working for the Associated Press news agency have been shot by a police officer in eastern Afghanistan, officials say.

One of the women, Anja Niedringhaus, died in the attack. Her colleague, Kathy Gannon, is reported to be stable.

The attack took place in the town of Khost near the border with Pakistan.

It comes as Afghanistan intensifies security ahead of presidential elections on Saturday, in response to threats of violence by the Taliban.

The new president will succeed Hamid Karzai, who has been in power since the 2001 fall of the Taliban but is constitutionally barred from seeking a third consecutive term.

Security presence

Photojournalist Anja Niedringhaus, 48, was killed instantly in the attack, the news agency confirmed.

Veteran reporter Kathy Gannon, 60, was said to be receiving medical treatment after she was wounded in the attack.

They came under attack whilst travelling with election workers delivering ballots in the Tanay district of Khost province.

An eyewitness said a police unit commander opened fire on the journalists as they were waiting for their convoy to move inside a security compound.

The police officer behind the attack was taken into custody after surrendering to other police, an interior ministry source said.

The district lies on the border with Pakistan's Waziristan region, with the Pakistan-based Haqqani network strong and influential in the area.

The Taliban has stepped up its attacks in recent weeks, in a bid to disrupt preparations for the election.

Last month, a senior reporter for Agence France-Presse, Sardar Ahmad, was killed alongside eight other people when Taliban gunmen attacked a hotel, which was popular with foreigners, in the Afghan capital of Kabul.

A journalist with Swedish and British nationality, Nils Horner, was shot dead in Kabul by gunmen on 11 March.

The BBC's Lyse Doucet in Kabul says the run-up to this historic poll has already been the bloodiest, and fears of electoral fraud are pronounced.

Nearly 200,000 troops have been deployed across the country to prevent attacks by the Taliban.

Key questions ahead of the vote What are the main issues? A final security agreement with the USA is the most pressing issue. All other matters, from trying to bring the Taliban to the negotiating table to fighting corruption and the drugs trade, depend on this Will the vote be free and fair? There is widespread concern about ballot stuffing and ghost polling stations - the kind of cheating that has marked every election since 2004 Is security a major logistical problem? Yes. The Taliban have vowed to disrupt the vote and there were a string of attacks leading up to it. But security at this election will be tighter than in previous votes What happens if no-one wins in April? If no candidate wins more than 50% of the vote, the two top contenders will go to a run-off on 28 May. As there is no clear front-runner, in contrast to 2009, a run-off is likely, with final results for the first round not expected until mid-May

Rings of security have been set up around each polling centre, with the police at the centre and hundreds of troops on the outside.

The BBC's Afghanistan correspondent David Loyn says the election is being protected by the biggest military operation since the fall of the Taliban.

Reporting restrictions are in place, limiting what can be broadcast about the candidates.

If nobody wins more than 50% of the vote in this round, a run-off election will be necessary.

There are eight candidates for president, including former Foreign Ministers Abdullah Abdullah and Zalmai Rassoul, and former Finance Minister Ashraf Ghani Ahmadzai.

Correspondents say the election may give the US a new chance to repair relations with Kabul, which are moribund after more than 12 years of war and repeated rows between the White House and President Karzai.

Relations between the president and Washington plunged to new lows late last year when the Afghan leader refused to sign a bilateral security agreement that would allow up to 10,000 troops to stay in his country after the Nato combat mission ends.