The decision to this effect was made at an emergent meeting of the Rabita Committee, said a statement issued by MQM here on Friday.
The Rabita Committee said that during the three-day mourning all political and organizational activities of the party will remain suspended and black flag will be hoisted in the party offices.
The MQM body has appealed to the masses to remain calm on the tragedy.
It has also appealed to the traders and transporters to keep their routine businesses activities continue.
The Rabita Committee has also appealed to party men to organize condolence meetings to condole and express solidarity with the bereaved family.
It has called upon the authorities concerned to immediately arrest the culprits.
MQM will observe Friday, Saturday and Sunday as mourning days.