UPDATE 1-Sudan, Chad trade accusations of aiding rebels

* Fighting fuels fears Doha peace deal could collapse

* Security Council condemns "external" aid for Chad rebels

* Sudan rejects allegations of supporting Chadian rebels (Adds Security Council statement, diplomats)

By Louis Charbonneau

UNITED NATIONS, May 8 (Reuters) - Sudan and its neighbor Chad accused each other on Friday of aiding rebels determined to topple their respective governments as fears grew that a new peace deal signed by Khartoum and N'Djamena could collapse.

The two countries signed an agreement in Doha this week in which they agreed to normalize relations and reject any support for rebel groups hostile to either of them. Days later they accused each other of breaking their word as fighting between government forces and rebels in eastern Chad intensified.

The U.N. Security Council issued a unanimous statement condemning what it described as military incursions "coming from outside" Chad -- which diplomats said referred to Sudan.

Chad's U.N. Ambassador Ahmad Allam-mi told a special meeting of the Security Council that his country had been misled by Khartoum into thinking that its neighbor would no longer support rebels intent on toppling his government.

"I have just arrived from Doha where, once again, I was naive enough to hope that the regime in Khartoum had decided to put an end to its attacks on my country, not to speak of its attempts to subvert or counter our policy to consolidate rule of law and democracy," he said.