General elections are being held in Pakistan for the first time since General Pervez Musharraf seized power in 1999. He has since changed the constitution in a way that many people fear is intended to allow him to retain power. But the president says he has launched comprehensive reforms and that the elections are part of his promise to restore democracy.

Sajid Iqbal of BBC Urdu Online looks at the key issues.

Who are the main contestants?

The main players include two leading political groups - the Pakistan People's Party of former Prime Minister Benazir Bhutto and the Pakistan Muslim League (PML-N) of another ex-Prime Minister, Nawaz Sharif.

A host of other groupings are also in the fray, including the Pakistan Muslim League Quaid-i-Azam (PML-Q) which supports the Musharraf government.

It comprises dissidents from the Nawaz faction of the Muslim League.

Two other groups are the Mutahida Majlis-i-Amal, which is an alliance of religious parties, and the National Alliance, which represents some smaller pro-Musharraf political parties (including former President Farooq Leghari's Millat Party).

Some regional parties are also expected to play a crucial role in the polls, including the Mutahida Qaumi Movement, which has a mass following in urban areas of Sindh province, and the Awami National Party, with a strong support base in the North-West Frontier Province.

Can everyone take part?

The Musharraf regime introduced several changes in election laws which disbar some of the prominent politicians including Mrs Bhutto and Mr Sharif.

The Representation of the People's Act includes a clause that prohibits convicted people from taking part in elections.

Another law forced several other politicians out of the contest as they did not have a bachelor's degree, a mandatory qualification.

How are the various representatives elected?

The election will decide candidates for the National Assembly, or lower house, of parliament.

Voters will also choose members of the four provincial assemblies.

Elections for the Senate, or upper house of parliament, are due on 12 November, when members of the provincial assemblies will elect senators for the four provinces.

Senators for the federally administered tribal areas will be held through direct elections.

Half of the senators will be elected for a three-year period and half for the full term of six years.

What are the main issues?

There is no single predominant issue. In urban areas - where only 30% of the population lives - President Musharraf's reform agenda has been the focus of much of the campaigning.

In rural areas, people are likely to take into account the past performance of candidates.

Tribal interests are also expected to influence the poll results significantly.

In the north and in the province of Baluchistan, religious parties will exploit anti-US sentiment.

Will the voting be free and fair?

Political parties and independent observers have expressed serious doubts about the impartiality of the Musharraf regime during the election campaign.

Some have alleged it is favouring the PLM (Q) and smaller groups represented in the National Alliance.

They say the government machinery and resources were abused by pro-Musharraf parties, a charge government officials deny.

Are the polls of interest to the international community?

Due to General Musharraf's stated commitment to democracy and his pivotal role in the US-led war against terror, the international community is watching developments in Pakistan very closely.

There are as many as 300 election observers from the European Union.

President Musharraf hopes a successful vote will establish his democratic credentials.

If pro-government parties prevail, it will also help boost his agenda for reform.