KHARTOUM, April 2 (Reuters) - Sudan on Wednesday accused Chad of violating its territory three times in the past 48 hours and, the latest in an exchange of accusations between the increasingly tense neighbours.

Sudanese Foreign Ministry spokesman Ali al-Sadig said a Chadian military Mirage jet flew over Sudanese territory in West Darfur on Tuesday.

On Wednesday morning a Chadian helicopter bombed a town called Um Kenjub, and in the afternoon the Chadian army fired a missile into a Sudanese military point.

"We consider these very serious violations and we cannot justify the attacks against Sudan," he said. "We are still exercising some restraint -- we don't want to respond."

But he warned: "Our army retains the right of self defence and to respond whenever they feel necessary."

Chad on Tuesday accused Sudan of being behind a rebel attack on Ade town in its arid east.

Sudan's Darfur region, which borders Chad, has been ravaged by five years of revolt, which in turn rekindled a civil war in Chad. Both governments accuse each other of supporting their insurgents.

Sadig rejected Chad's accusations on Tuesday that Chadian rebels had backing from Khartoum in the Ade raid, calling it an attempt to cover up for N'Djamena's attacks on Sudan.

Last month the two African oil producers signed a deal in Senegal to end attacks across their long, porous and unmarked border.

A European border monitoring force patrolling in eastern Chad accidentally crossed into Sudan in March, sparking and exchange of fire with Sudan's army. A French soldier was killed. (Reporting by Opheera McDoom, editing by Mary Gabriel)

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