FACTBOX: Profiles of key Afghan presidential candidates

KABUL (Reuters) - Afghanistan holds presidential and provincial elections on Thursday, the second since the Taliban were overthrown in 2001, with attacks mounting and insurgents vowing to disrupt the poll.

There are 35 candidates, among them two women, challenging incumbent Hamid Karzai, who must win more than 50 percent of the vote to avoid a run-off against a second-placed candidate.

Two recent U.S.-funded polls showed Karzai winning about 45 percent of the vote, compared with 25 percent for former foreign minister Abdullah Abdullah.

Following are brief profiles of some of the leading candidates:

* Hamid Karzai, leader of Afghanistan since the Taliban's ouster and the man who won the country's first presidential poll in 2004:

Karzai, 51, is an ethnic Pashtun from the same tribe as the former Afghan royal family. He received a Masters Degree in political science in India in 1983 and then joined a small pro-monarchist faction of the anti-Soviet mujahideen in Pakistan.

He served as deputy foreign minister after the fall of the Soviet-backed government in Kabul in 1992.

At first supporting the Taliban, Karzai later worked from Pakistan to overthrow the austere Islamists. He returned to Afghanistan in late 2001 when he was appointed president of the country's interim government in a U.N.-sponsored deal in Germany.

Endemic government corruption, slow development, his alliance with former militia leaders and civilian casualties caused by foreign forces have eroded his public support. Karzai says talks with the insurgents are his top priority.

* Abdullah Abdullah, Afghan foreign minister, 2001-2006:

The 48-year-old Abdullah has a medical degree from Kabul University and worked as an ophthalmologist until 1985. A year later he joined the Panjshir Resistance Front against the Soviets and served as an adviser to the late Ahmad Shah Masood.

Abdullah was foreign minister of the Northern Alliance from 1998 onwards and, after Masood's assassination in 2001, became a dominant figure in the alliance that helped U.S. forces in toppling the Taliban.

He was appointed foreign minister under Karzai's interim government, a position he held until Karzai sacked him abruptly in 2006. He is seen as a prominent leader of the ethnic Tajiks in the north but is also half Pashtun.

Abdullah is pushing for the establishment of the post of prime minister and for the election of governors and mayors.

* Ashraf Ghani, a senior fellow in foreign policy at the Brookings Institution and finance minister, 2002-2004:

The 59-year-old Ghani, an ethnic Pashtun, received a PhD in anthropology from Columbia University. Ghani has spent more than two decades outside Afghanistan, working at different universities and for the World Bank.

In 2002, he served as special adviser to the United Nations and later as finance minister under Karzai. In 2005, Ghani founded the Institute of State Effectiveness in the United States aimed at promoting effective government. Ghani used to live in the United States.

* Ramazan Bashardost, member of parliament and planning minister, 2004 to 2005:

Regarded as ascetic, the 43-year-old Bashardost is an ethnic Hazara who spent more than 20 years in France, where he received Masters Degrees in law, diplomacy and political science and a PhD in law.

Openly criticizing the government and accusing ministers of corruption, Bashardost has modeled himself as a man of the people. While briefly serving as planning minister, Bashardost was critical of the role of aid agencies in Afghanistan and later resigned under government and foreign pressure.

Bashardost runs his campaign from a tent opposite parliament and has vowed not to allow foreign troops to stay in Afghanistan if elected.

* Mullah Salam Rocketi, a former Taliban commander who now sits in the parliament. He earned the nickname of Rocketi for firing rocket-propelled grenades and Stinger missiles during the war against the Soviet occupation.

An ethnic Pashtun, Rocketi, 51, is seen as a strong negotiator and was among a group of former Taliban members who went to Saudi Arabia last year to meet King Abdullah as part of Karzai's effort to persuade the Taliban to join peace talks.

* Hedayat Amin Arsala, an economist and a prominent Afghan politician. He was the first Afghan to join the World Bank and served there for 18 years.

He served as foreign minister for two years in the early 1990s when he was Karzai's boss. Arsala, 67, is also a Pashtun and was senior minister until recent months.

* Frozan Fana, 40, is one of only two female candidates and a surgeon who spent some years in self-imposed exile in Europe. Her husband was a minister in Karzai's government until he was killed at Kabul airport in 2002.

Fana says she also wants to hold talks with any Taliban fighters who agree to lay down their weapons.