A powerful bomb blast rocked a busy commercial district in Ankara on Tuesday, killing five people and injuring about 60 others, officials in the Turkish capital said.

The explosion blew out the entrance of a shopping centre and shattered several windows on the five-storey building in the downtown district of Ulus. The windows of nearby buildings and a bus shelter were also destroyed by the force of the blast.

The bomb, placed in front of a shopping centre, killed five people and injured 60 others.
(Associated Press)

Those killed included four Turks and one Pakistani, Prime Minister Tayyip Erdogan said. He did not point the blame at any particular group and no one has claimed responsibility for the attack.

"We have seen a vicious, ruthless terror attack at Ankara's busiest time," Erdogan told reporters, adding that authorities were still investigating the type of bomb used.

Turkey's NTV television station said plastic explosives had been placed beside a bus stop during the evening rush hour.

NTV also quoted police sources as saying the rebel Kurdistan Workers' Party (PKK) was a suspect in the attack. The group is waging an armed struggle for greater Kurdish rights in Turkey.

Last September, suspected Kurdish rebels set off a bomb at a bus stop in Turkey's largest majority Kurdish city of Diyarbakir, killing 10 people.

Police have detained seven people in connection with Tuesday's bomb blast, NTV said.

Television video showed medics tending to the injured and carrying people into ambulances on stretchers. A body covered in a white sheet could be seen lying outside the shopping mall.

The explosion came as Turkey prepares for early legislative elections in July, called by the government amid a political crisis caused by a standoff between secular and Islamist forces over who will be the country's next president.

With files from the Associated Press