By Pascal Fletcher

DAKAR, May 26 (Reuters) International rights groups appealed to the United Nations today to put ''rhetoric into action'' by deploying a robust peacekeeping force in Darfur by October 1 to halt attacks on civilians they blame mainly on Sudan.

''Darfur's most urgent need is for a significantly stronger international force to be deployed without delay,'' Amnesty International, Human Rights Watch and the International Crisis Group think tank said in a joint letter to the Security Council.

Sudan is under intense international pressure to accept a beefed-up UN peacekeeping force in its western Darfur region to end three years of political and ethnic conflict there that has killed tens of thousands and is spilling over into Chad.

In a related move, a UN refugee official said talks were under way with the European Union about the need for a smaller separate force in eastern Chad to protect camps sheltering Darfur refugees from attack by marauding militia and rebels.

''Janjaweed'' militia, ruthless raiders on horses and camels who are allied to Sudan's Arab government, have killed, raped and looted across Darfur since 2003 and are now striking deeper and deeper into eastern Chad by attacking villages there.

A Human Rights Watch report released yesterday said 118 eastern Chadian villagers were shot and hacked to death by the Janjaweed and local Chadian recruits in a mid-April massacre.

''The arrival of the (UN) blue helmets in Darfur is essential,'' Ana Liria-Franch, representative in Chad of the UN refugee agency UNHCR, told Reuters.

She said a UN force in Darfur would help halt ross-border incursions by the Janjaweed and Sudanese and Chadian rebels.

After initially refusing, Sudan has said it will negotiate with the UN the possibility of an expanded force to take over from hard-pressed African Union peacekeepers in Darfur, whose mandate expires at the end of September.

Amnesty, Human Rights Watch and Crisis Group praised a recent Security Council resolution affirming the world's responsibility to protect populations from genocide, war crimes, ethnic cleansing and crimes against humanity.

But victims like those in Darfur would benefit ''only if it is transformed from rhetoric into action,'' they said.

EAST CHAD PROTECTION FORCE They urged a ''broad and robust mandate'' for the UN Darfur force to protect civilians.

Liria-Franch said that while UNHCR saw the UN deployment in Darfur as key to overall security in the region, their camps holding 220,000 Darfur refugees in east Chad needed immediate additional security against Janjaweed and rebel attacks.

Security at these 12 camps was being provided by around 235 Chadian gendarmes - soon to be reinforced by 100 more - but this was not enough.

''We're considering a European force, about 450-strong,'' she said, adding UNHCR was consulting with UN Secretary-General Kofi Annan and the European Union. French troops in Chad could be part of this.

A Spanish UN staffer was shot and badly wounded in eastern Chad this month and the UN warned today it may have to suspend work at some camps there unless the host government tightened security to stop rebels from entering to recruit.

Amnesty, Human Rights Watch and Crisis Group said Security Council members must immediately secure the Sudanese government's consent to a UN force in Darfur or impose further sanctions on high-level Sudanese officials.

They called Sudan ''largely responsible for the catastrophe that has become Darfur and now threatens Chad''.

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