Hiiraan Online

South Africa's Nkosazana Dlamini-Zuma is challenging the sitting chairman of the commission, Gabon's Jean Ping, after neither won the required two-thirds of the vote at the last summit six months ago, leaving Ping in the post.

Security issues are a top priority at the meeting, with leaders focusing on instability in Mali, renewed violence in the Democratic Republic of Congo and the ongoing crisis between Sudan and South Sudan.

Ping opened the summit saying that the AU was ready to send troops to the restive eastern DR Congo as part of a peacekeeping force, where Rwanda is accused by UN experts and Kinshasa of supporting a mutiny by Congolese troops.

"The AU is prepared to contribute to the establishment of a regional force to put an end to the activities of armed groups," Ping told African leaders, including DR Congo President Joseph Kabila and Rwanda's Paul Kagame.

Rwanda has denied involvement and in turn accuses Kinshasa of renewing cooperation with Rwandan Hutu rebels, who have been based in eastern DR Congo since the 1994 Rwandan genocide.

But Ping also warned that other African hotspots remained a major concern, with the ongoing crisis in Mali "undoubtedly one of the most serious threats to security and stability of the continent."

The warning follows meetings by African leaders on Saturday, where they called for a speedier political transition as Mali's interim government struggles to tackle Islamist militants holding the vast desert north.

"The situation in the north of Mali... is alarming and is a threat to the region and beyond," said Jan Eliasson, the UN Deputy Secretary-General.

"We must also continue working together, as well as with the transitional government, to restore territorial integrity and security."

More hopeful areas include Somalia -- where Islamist fighters are on the back foot -- and the disputes between Sudan and South Sudan, following fierce border battles in April and March along disputed regions of their oil-rich frontier.

Sudanese President Omar al-Bashir and Salva Kiir of South Sudan shook hands warmly as leaders filed into meeting, following their first face-to-face talks on Saturday since the border fighting took them to the brink of all-out war.

Ping noted "with satisfaction the end to the fighting and advances made recently" in talks between Juba and Khartoum, who have been holding months of slow-moving AU-led talks to resolve a raft of contentious issues.

"Their people desperately hope for security and prosperity, we have a common duty not to shatter their hopes," Eliasson added.

For once, Ping noted positive changes in war-torn Somalia, praising the nations who had sent troops to battle the Al-Qaeda linked Shebab, including Burundi, Djibouti, Kenya and Uganda in the 17,000-strong AU force, as well as Ethiopia.

"The prospects for peace have never looked so encouraging," said Ping.

However, the AU leadership race is expected to dominate proceedings later in the day, and both candidates have issued strongly worded public statements ahead of Sunday's vote.

Analysts say unwritten tradition is that continental powerhouses do not run for the post -- leaving smaller nations to take the job -- and that South Africa's decision to override this rule has sparked bad feeling.