* AU has only $5 million in funds for troops
* EU promises 25 mln euros for troops, 20 mln for elections
* "Massive violations" in C. African Republic -U.N. official
* Unsigned email says new group to defend northern interests (Adds quotes, anti-government statement)
By Aaron Maasho and Edmund Blair
ADDIS ABABA, Jan 31 (Reuters) - The United Nations is asking donors for more money to fund African Union peacekeepers trying to end inter-communal violence in the Central African Republic, a U.N. official said on Friday.
Almost a million people, a quarter of the population, have been displaced by fighting since the mostly Muslim Seleka rebel group seized power last March in the majority Christian country. At least 2,000 people are estimated to have been killed.
"It is a critical situation. We have seen massive violations of human rights and violations of international humanitarian law," U.N. Deputy Secretary-General Jan Eliasson told Reuters, speaking on the sidelines of an African Union summit.
The United Nations has warned that the conflict in the landlocked former French colony risks spiralling into genocide.
One focus of the conflict on Friday was the town of Sibut, a gateway to the north of the country. Seleka fighters arrived there mid-week and there have been reports of killings, a senior international aid worker said.
"They (Seleka) have regrouped in Sibut. They are armed elements who have lost power and are trying to reconfigure," said the aid worker, adding that the situation could lead to a de facto partition of the country.
In a possible sign of this, an unidentified group said it was forming a new body, the Independence Movement of northern Central African Republic.
The group's aim is to protect the interests of that region in the face of oppression and neglect, according to a statement published on a local news website on Friday.
"This movement gathers all the active forces in north Central African Republic as a whole without religious, regional or ethnic distinction and aims at ... the total liberation of north Central Africa from southern domination," the email said.
Its veracity could not be independently confirmed but Peter Bouckaert, emergencies coordinator at Human Rights Watch who is currently working in the country, said it could be authentic.
Eliasson said the priority was to support the African force, known as MISCA, adding that a trust fund set up to finance it had "only slightly over $5 million". He said he had no set target for a meeting of donors in Addis Ababa on Saturday.
MISCA has more than 5,000 soldiers in the Central African Republic, where a 1,600-strong French force is also deployed.
The European Union, which has promised to send 500 soldiers, said on Friday it was ready to put 25 million euros ($34 million) into the MISCA fund and provide another 20 million euros for the country's electoral process.
EU development commissioner Andris Piebalgs said the extra money would bring total EU commitments to the Central African Republic since the crisis began to about 200 million euros.
MISCA aims to raise the number of troops deployed by March to about 6,000, an African official said, the current ceiling for the force, although France has said more are needed.
Eliasson said the number of peacekeepers needed would depend on political progress, helped on this month when a transitional assembly elected Catherine Samba-Panza as interim president.
"This situation cannot be solved only by a military or peacekeeping operation," Eliasson said.
He said fund-raising was hard, given a host of demands on donors, including the latest $6 billion U.N. appeal for Syria.
African Union director of peace and security El Ghassim Wane said MISCA had 5,300 troops on the ground and expected 700 from the Democratic Republic of Congo for a total of 6,000. Rwanda, Burundi, Chad, Cameroon and others have already sent troops.
"I can assure you that by the end of the programme in March we will have all troops on the ground," Wane told Reuters.
France has called for a U.N. peacekeeping force. Its U.N. Ambassador Gerard Araud said transforming the African Union force into a U.N. operation would bring guaranteed funding.
The World Food Programme, a U.N. agency which has provided food aid to 220,000 people displaced by the crisis since the start of the year, also appealed for more money on Friday.
($1 = 0.7373 euros) (Writing by Edmund Blair and Bate Felix; Additional reporting by Matthew Mpoke Bigg and David Lewis; Editing by Matthew Mpoke Bigg and Gareth Jones)