The Baluch Liberation Army (BLA) has claimed responsibility for the two attacks in Quetta on Sunday.
In a statement circulated to local media, a BLA spokesman warned of more attacks related to Pakistan's independence day celebrations.
On Sunday, unidentified attackers lobbed a hand grenade at a stall selling Pakistani flags ahead of the country's upcoming independence day on August 14. The stall owner was injured in the attack.
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"BLA has claimed responsibility for twin attacks in #Quetta today. They say both were targeted attacks. #BLA has warned people from celebrating Independence Day in Baluchistan," said Suhaib Zuberi on twitter.
At least two policemen were killed and eight others injured in an explosion near Quetta's Serena Hotel, a luxury hotel, on Sunday evening.
Pakistan media reports said four passers-by were also wounded in the blast that targeted a police mobile near Tanzeem Chowk, Balochistan government spokesperson Liaquat Shahwani said in a statement.
He said the bomb was fitted into a motorcycle. The injured were shifted to A hospital, where an emergency was imposed.
He condemned the attack, saying "terrorists want to disturb Balochistan's peace and spread fear".
"[We] will bring to justice the elements trying to create disturbance in peaceful Balochistan," he added.
The incident comes more than three months after a powerful bomb exploded in the parking lot of the Quetta Serena Hotel, killing five people and wounding a dozen others.
Pakistan Taliban had claimed responsibility of blast at Serena Hotel in April.
Police said that the explosion on Sunday took place at Zarghoon Road, near the city's University Chowk, adding that the explosives were planted on a motorcycle. The explosion took place near a police van.
The injured, including two policemen, were shifted to the city's Civil Hospital, Deputy Inspector General Quetta said, adding that the windows of nearby buildings were shattered due to the explosion. Chief Minister of Balochistan Jam Kamal Khan has condemned the incident.