The head of Pakistan's anti-corruption bureau says it has decided not to arrest Prime Minister Raja Pervaiz Ashraf, despite orders to do so by the supreme court.

Fasih Bokhari, chief of the National Accountability Bureau, told the court Thursday that he does not have sufficient evidence to arrest Mr. Ashraf on corruption charges.

On Tuesday, the supreme court ordered the arrest of the prime minister and 15 others on charges involving private power stations.

Mr. Ashraf is accused of taking bribes for arranging to build power plants to serve Pakistan's power deficiency. Mr. Ashraf has denied the allegations.

Observers say the arrest warrants could worsen the already-existing tension between the government and the courts.