ISLAMABAD - At least 21 people were killed and over 40 others injured when a twin bomb attack hit Pakistan's southwestern city of Quetta on Wednesday morning, reported local Urdu TV channel Geo.

Three children, two security personnel, a senior local paramilitary officer's wife were reportedly among those killed in the attack. At least five cars including two vehicles of security forces and four buildings were damaged, said local media reports.

All the injured people have been shifted to nearby hospitals. The injured people included a local senior paramilitary officer. Five of the injured people are in critical condition, said hospital sources.

So far no group has claimed responsibility for the attack yet.

The twin bomb attack took place at about 9:00 am Wednesday before the office hour in front of the office of Quetta District Commissioner Naseem Lehri.

The first bomb, which was fixed on a rickshaw parked in front of the commissioner's office went off when the commissioner Naseem Lehri was on his way to the office in his car. The commissioner remained safe in the attack, said the reports.

As people rushed to the blast site, a suicide bomber under the help of two gunmen launched an attack at a local senior paramilitary officer's living compound adjacent to the commissioner 's office.

The unknown gunmen opened fire at the security people guarding in front of the compound. After the suicide bomber forced into the compound with the help of the gunmen who later run away, he was stopped by people inside the compound. The suicide bomber blew himself up before he reached inside the house, said local reports.

The house belongs to Deputy Inspector General Frontier Corps Brigadier Farrukh Shehzad who is said to be in charge of a recent operation which resulted in the arrest of a senior al-Qaida leader named Younas Al Moritani in Quetta. Shehzad's wife was killed in the blast, but Shehzad himself and his children were only injured in the blast.