"This is an important turning point in the Darfur conflict," said Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani, whose country hosted a week of talks between the Khartoum government and the Justice and Equality Movement.

"I am very optimistic, as both sides are determined to end this conflict," he said at a press conference following the signing.

The Doha talks were the first contacts since 2007 between the government and representatives of JEM, which boycotted another largely abortive Darfur peace deal in 2006.

"We will reach a final and just solution with God's will, to end this war, which with God's will will be the last war in Sudan," JEM leader Khalil Ibrahim said at the press conference.

He said that "in a sign of goodwill," the JEM would release a number of prisoners from the government side. Sudanese officials did not announce a similar move.

Ibrahim said the JEM is keen to include all warring factions in the negotiations, and called on Sudan's neighours Chad, Egypt, Libya and Eritrea as well as the international community to join the talks.

The sponsors of the Doha talks - Qatar, the United Nations, African Union and Arab League - stressed that they were preliminary and intended to pave the way for a broader peace conference on Darfur.

"The two sides have committed themselves in principle to an exchange of prisoners, to be freed in successive groups between now and the launch of talks on a framework agreement on peace in Darfur," JEM member Tahar el-Fakih said on Monday.