Police and residents help injured people lying on the street after an explosion rocked a shopping mall in Ankara May 22, 2007. [Photo: Reuters]

A deadly explosion occurred in a busy shopping center in Turkey's capital city of Ankara on Tuesday, leaving six people dead, including a Pakistani national, and more than 80 others injured.

The private NTV television channel quoted police sources as reporting that the explosion was caused by A-4 plastic explosives, commonly used by the outlawed Kurdish Workers' Party (PKK).

Turkish Prime Minister Recep Tayyip Erdogan, who visited the scene of explosion in Ulus district, strongly condemned the bombing.

"We have seen a vicious, ruthless terror attack at Ankara's busiest time. Although our security forces have taken all necessary measures, this event occurred," Erdogan said.

Erdogan noted that security forces were searching the rubble for clues.

The PKK, which was listed as a terrorist organization by Turkey, the United States and the European Union, have staged similar attacks targeting civilians in the past.

"The explosion ... revealed once again that we all should unite against terrorism. We have to create a global platform against terrorism," Erdogan stressed.

According to the semi-official Anatolia news agency, eight Pakistani nationals, who were in Ankara to attend the Eighth International Defense Industry Fair, are among the injured. However, none of them are in critical condition.

A crisis center was established at the Ankara Governor's Office upon directives of Prime Minister Recep Tayyip Erdogan after the explosion, Anatolia said.

Meanwhile, Turkish Red Crescent urgently sent 150 units of blood to hospitals.

The Red Crescent also deployed specialized psychologists and emergency situation experts at the scene of the explosion.

Moreover, Turkish State Minister and Deputy Prime Minister Mehmet Ali Sahin said that all security forces were on alert.

According to Anatolia, a suspect person was detained in connection with the explosion.

The attack came as security forces launched a large-scale military operation against the Kurdish rebels in the country's eastern and southeastern regions.

More than 30,000 people have been killed since the group launched an armed campaign for an ethnic homeland in the mainly Kurdish southeastern Turkey in 1984.