At least 39 people were injured in a grenade attack on a Jamaat-i-Islami rally in Karachi on Wednesday evening, officials said.

The blast took place near the main truck that was part of the rally in Gulshan-i-Iqbal area, a JI spokesperson said.

Of the total, one person was stated to be in critical condition while no deaths were reported, according to Meeran Yousuf, the media coordinator to the Sindh health minister.

She earlier said five of the injured were taken to Al Mustafa Hospital, seven to the Jinnah Postgraduate Medical Centre (JPMC), 11 to Aga Khan University Hospital and 10 to Liaquat National Hospital.

According to Yousuf, a majority of the injured received "very minor injuries", while some were discharged.

East Senior Superintendent of Police Sajid Sadozai said two unidentified persons riding a motorcycle threw an RGD-1 grenade at the rally and fled.

He had earlier ruled out that the blast was caused by a planted bomb.

The explosion, which took place near Bait-ul-Mukarram Masjid, also shattered the windows of nearby cars. A heavy contingent of police and Rangers reached the site after the blast.

The banned Sindhudesh Revolutionary Army (SRA) claimed responsibility for the attack through social media.

The JI rally was being held in connection with Youm-i-Istehsal (the day of exploitation), which is being observed today to mark one year since India revoked occupied Kashmir's semi-autonomous status on August 5.

In a tweet, JI chief Sirajul Haq termed the bomb attack a "cowardly act".

"Indian agents are still present in the city who could not tolerate the expression of solidarity with the people of Kashmir," he said. "We will not be frightened by such vile acts and will speak up for the people of Kashmir with increased determination."

JI spokesperson Zahid Askari said the rally continued after the blast and it was addressed by JI Karachi chief Hafiz Naeemur Rehman at Hasan Square. In his speech, Rehman condemned Indian atrocities against Kashmiris and the attack on the rally and demanded the arrest of the culprits.

Sindh government spokesperson Murtaza Wahab condemned the attack, terming it a "conspiracy to disturb the peace of Karachi".

He said "anti-state forces" were carrying out such acts to achieve their vile objectives.

3 hurt in cracker blast

In a separate incident, three people were injured in what police described as a cracker attack in the city's Korangi area. Unidentified miscreants riding a motorcycle hurled a homemade grenade at an estate agency at Nasir Jump, Korangi-I and fled.

The incident left three men injured who were shifted to the JPMC.

Dr Seemin Jamali said one of the three men suffered wounds in his eye while another received injuries on his chest. All of them were in stable condition.

Police in their initial probe ruled out the possibility of a terrorism motive behind the incident. They said it appeared to be the outcome of some personal enmity.