Two blasts on Wednesday left two people dead and six others wounded in Pakistan's financial capital of Karachi, police said.
"A bomb, apparently planted in a motorcycle, exploded in Karachi's eastern neighbourhood of Sohrab Goth, killing two people and wounding two others," Safdar Ali, a local police official told sources.
Ali said the bomb exploded minutes after a hand grenade was hurled at a police van, a kilometre away.
"Around 30 minutes before the bomb explosion, two persons came on a motorbike and hurled a grenade on a police van. Three policemen and one civilian were injured in the explosion caused by the grenade," he said.
Another official said police were trying to identify the victims.
"We are gathering details of both events. We suspect that the two people killed in the second incident may be the terrorists trying to plant the bomb," Abdul Kareem Mughal, a senior police official, told sources.
The city of 18 million, which is Pakistan's business hub, is routinely affected by violence.
Last year around 2,000 people were killed in violence linked to ethnic and political tensions, the deadliest toll in two decades.