ADDIS ABABA, May 29 (Reuters) - Ethiopian police have arrested five suspects thought to be behind a blast in the country's volatile Ogaden region that killed 11 people and wounded the local president, state media reported on Tuesday.

Five people were killed by at least one explosion and six others, mostly children, were crushed to death in a stampede after Monday's attack tore through crowds celebrating a national holiday in the eastern region's capital Jijiga.

The government blamed the strike on the Ogaden National Liberation Front (ONLF), separatist rebels who last month raided a Chinese-run oil exploration field in the area, also known as the Somali region, killing 74.

"The Somali State Police Commission ... has apprehended five alleged Eritrean regime-sponsored terrorists that threw (a) hand grenade on the residents of Jijiga," the official Ethiopian News Agency (ENA) said. Fifty-two people had been injured, it said.

Witnesses said local president Abdullahi Hassan suffered a leg wound and was thrown through the air by the blast. Dancers and musicians gathered around him were among the dead.

The ONLF has denied involvement in Monday's attack, saying the movement does not target civilians, only Ethiopian troops.

Amid contradictory reports, the government also blamed the rebels for a booby-trap blast elsewhere in Somali state that a senior official in Addis Ababa said had killed five people.

ENA quoted police as calling on the members of the public to continue exposing "anti-peace elements" in the remote region.

The area has been wracked by a sporadic but long-running conflict between government forces and the ONLF, which wants more autonomy for the under-developed lands bordering Somalia.

Ethiopia has long accused its neighbour and arch-foe Eritrea of training and arming the ONLF. Asmara denies that.

Tension mounted sharply in April when ONLF fighters killed 65 Ethiopians and nine Chinese oil workers in a raid on an oil field near Abole, some 120 km (75 miles) south of Jijiga.

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