Turkish police and media say a bomb has exploded near the offices of the country's ruling party in Istanbul.

The chief of Istanbul's police department was quoted saying several police officers were injured in the explosion early Thursday.

State-run television showed pictures of ambulances and fire engines rushing to the scene outside the offices of Prime Minister Recep Tayyip Erdogan's ((AK) Justice and Development Party.

It said the bomb was mounted on a motorbike and that a police bus and another vehicle were damaged by the blast.

No one immediately claimed responsibility for the blast. However the government faces harsh criticism from several groups, including Kurdish rebels, leftists and Islamist militants.