Five bombs ripped through a police training school in southwestern Pakistan early Thursday, killing six policemen and wounding nine, a police official and doctor said. Two people were arrested.

The bombs had been planted at a firing range on the grounds of the police school in Quetta, capital of the southwestern Baluchistan province, senior Quetta police official Wazir Nasar said.

Two ethnic Baluch tribesmen were detained near the scene and were being questioned on suspicion of involvement in the blasts, Nasar said.

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Frequent attacks on security forces in Baluchistan are blamed on tribesmen who are trying to extract more royalty from the government for resources taken from their area.

Four of the injured were seriously hurt, said Mohammed Abdullah, a doctor at the state-run Civil Hospital in Quetta.

"We received six bodies and nine injured people," he said.

An Associated Press reporter also saw the six bodies, some of them with blown-off limbs.

The explosions may have been caused by land mines, Salman Shah, another Quetta police official, said on Pakistan's Geo television.