The gunmen opened fire shortly after Friday prayers and threw grenades at two Ahmadi worship places in Lahore’s Model Town and Garhi Shahu neighbourhoods.
Rizwan Naseer, director general of an ambulance service, told Reuters 30 bodies had been taken to hospitals in the city.
City officials had earlier put the death toll at 14.
“There are some hostages and we are planning an attack,” said Haider Ashraf, a senior police office in the neighbourhood of Garhi Shahu. “Their lives are under threat.”
Shooting continued at Garhi Shahu.
There was no immediate claim of responsibility, but suspicion quickly fell on the Pakistani Taliban.
“The operation is not even over yet, so it’s too early to say who is behind these attacks. But my guess is that like most other attacks, there would be some link to the Taliban or their associated militants,” said a Lahore-based security official.
In Model Town, police said one gunman had been arrested and another killed.
“The prayer leader was giving a sermon when we heard firing and blasts. Everybody stood up and then two gunmen barged into the place of worship and sprayed bullets,” Fateh Sharif, a 19-year-old student, told Reuters from Model Town.
“They had long beards. They were carrying rucksacks.”
Lahore's deputy commissioner Sajjad Bhutta said a suicide vest packed with explosives was recovered from the worship place in Model Town, where some attackers escaped. One fired at a television van before the area was made safe.
“He was young, clean-shaven. He sprayed bullets at our van while fleeing the scene,” Rabia Mehmood, a reporter for Express Television, told Reuters.
Attacks launched after prayers
Witnesses said the assaults were launched shortly after prayers.
“I saw some gunmen run towards the Ahmadis' place of worship and then I heard blasts and gunfire,” Mohammad Nawaz, a resident, told Reuters.
Ahmadis are a minority religious community founded in the late 19th century. They hold unorthodox beliefs, including that Jesus Christ survived the crucifixion and died in Kashmir.
Some also believe that prophets have come after Prophet Mohammad but that he retains his primacy.
Pakistan is the only Muslim state to have declared Ahmadis non-Muslims. Its four million-odd members have seen their religious rights in overwhelmingly Muslim Pakistan curtailed by law.
Pakistan, a key US ally in the fight against militancy, is often the scene of sectarian violence, with militants from Sunni Muslim groups attacking Shia Muslim and Christian communities.