Sudanese government envoys and rebel leaders from the western province of Darfur have formally opened peace talks in Nigeria's capital, Abuja.

Members of the Sudanese government along with negotiators from the two main rebel groups in Darfur are meeting in the Nigerian capital to work out a peace agreement to end almost two years of fighting between the pro-government Arab janjaweed militia and rebel groups operating in the province.

Three weeks of talks held last month in Abuja ended in failure.

The United Nations estimates the fighting in Darfur has claimed tens of thousands of lives and caused more than a million people to flee their homes.

The new round of talks is complicated by the emergence of two new rebel movements in the Darfur region. Although little information is currently available about the new groups, there is widespread concern because they are not part of a ceasefire agreement the government and the Sudanese Liberation Army and the Justice and Equality Movement signed earlier this year.

African Union troops are on the ground in western Sudan to monitor the ceasefire and assist in getting aid to civilians. The Nigerian commander in charge of the AU troops in Darfur, Major General Festus Okonkwo, says one of the new rebel groups is a breakaway faction of the Justice and Equality Movement, but is believed to be working with the government in Khartoum.

Currently there are fewer than 500 AU troops in Sudan, but the number is expected to grow to more than three thousand by the end of the year.

The U.N. Security Council has threatened to impose sanctions against the Sudanese government if the situation in Darfur does not improve. There will be a special meeting of the Security Council in the Kenyan capital Nairobi next month to discuss the crisis.