* Samba Panza hails talks as first step in peace process
* Forum due to last three days in presence of mediators
* Human Rights Watch urges no Amnesty for rights violators (Adds quotes from President, militia coordinator)
By Christian Elion
BRAZZAVILLE, July 21 (Reuters) - Central African Republic's interim president appealed on Monday to Muslim Seleka rebels and 'anti-balaka' Christian militia to agree on a ceasefire at the start of talks in the neighbouring Congo Republic.
The three-day forum in Brazzaville, mediated by Congolese President Denis Sassou Nguesso, aims to reach terms for a halt to hostilities and disarmament but will not address negotiations for a longer-term peace deal in the former French colony.
"This forum which opens today is a major step in the political dialogue and reconciliation between the sons and daughters of Central African Republic," Interim President Catherine Samba-Panza said at the opening of the talks.
Samba-Panza, whose government will steer the country to elections next year, said the forum would pave the way towards further difficult steps in securing peace, such as inter-community talks at a grassroots level.
"It is time to lay down arms," Samba-Panza said.
She appealed to all parties to embark on the path of a peaceful and political solution.
The talks bring together some 169 delegates from the transitional government, civil society and armed groups.
Thousands have been killed and more than a million forced from their homes by sectarian violence which erupted after mostly Muslim Seleka fighters seized power in the majority Christian country in March 2013.
Months of looting and killings by Seleka fighters - many of them mercenaries from neighbouring Chad and Sudan - prompted a backlash by the 'anti-balaka' militia that has driven the rebels and tens of thousands of Muslims northwards, effectively dividing the country along religious lines.
Clashes between the two sides and reprisals against both Christians and Muslims have continued despite the presence of 2,000 French peacekeepers and 6,000 African troops. The United Nations will deploy a peacekeeping mission in September.
"READY TO DISARM"
Samba-Panza said the results of the Brazzaville forum will depend on actions on the ground at all levels to encourage reconciliation.
The coordinator for the anti-balaka militia, Patrice Edouard Ngaïssona, said he was hopeful of progress.
"I am ready to lay down my weapon, so too other anti-balaka members," Ngaïssona said.
"It has already started with some of our ex-Seleka brothers. But certain conditions especially about foreign mercenaries need to be addressed in Brazzaville before a definitive return to peace in Central African Republic," he said.
Samba-Panza took office after Seleka leader Michel Djotodia was forced to resign as president in January under international pressure.
Djotodia, who was reappointed as Seleka leader this month, is the target of U.S. sanctions and will not personally attend the talks.
Human Rights Watch appealed on Sunday for participants in the forum to reject any calls for amnesty for those responsible for serious human rights abuses.
"Mediators need to make clear that lasting peace cannot be achieved without justice and that no one is above the law," said Daniel Bekele, Africa director at Human Rights Watch.
In a sign of the volatility of the situation, several Seleka fighters awaiting disarmament took to the streets of central Bangui on Monday, firing into the air, after one of their number was stabbed by a militia member. Calm returned after French and African peacekeepers deployed to the area. (Writing by Daniel Flynn and Bate Felix; Editing by Angus MacSwan)