The deadliest attack Saturday took place in the provincial capital of Quetta and appeared to target minority Shiites. A blast ripped through a bus carrying female university students, killing at least 14 people, said the head of police operations, Fayaz Sumbal.
The victims and bodies were rushed to a nearby hospital. As relatives, rescuers and government officials crowded into the building, a suicide attacker detonated explosives in the corridor leading to the emergency room, Sumbal said.
Other attackers then began firing at the crowd, prompting dozens to hide inside the hospital while others fled into the parking lot.
Soldiers and police commandos rushed to the scene and penned the attackers off into a wing of the hospital, Sumbal said.
An Associated Press reporter nearby heard intermittent gunfire as troops took up positions around the building. As fighting continued into the evening, another loud explosion later determined to be one of the attackers blowing himself up shook the hospital. Inside, patients, visitors and staff hiding behind locked doors spoke of the firefight.
"Everybody is trying to take shelter in the corners, behind the steel cupboards and tables," Hidayatullah Khan, who had been visiting a niece wounded in the earlier bus bombing, told the AP by telephone.
A high-ranking government official who had been visiting wounded in the hospital died in the blast, as did two nurses, said Sumbal.
Another four soldiers from the country's Frontier Corps also died, said Interior Minister Chaudhry Nisar Ali Khan. But it was not clear whether they were killed in the explosion or in the ensuing operation to clear the building. He said at least 35 people trapped inside the building were freed.
Six of the attackers died during the siege four killed by security forces and two others who blew themselves up, Sumbal said, adding that thirty people were wounded from their gunfire.
Lashkar-e-Jhangvi, a group of radical Sunni Muslims, who revile Shiites as heretics, claimed responsibility for the attack on the school bus and the hospital. The group said one of their female suicide bombers blew up the bus because it was carrying Shiites, although officials said the bus was also carrying students from other religious and ethnic groups.
The group has claimed responsibility for numerous attacks against Shiites, including a bombing in Quetta in January that killed 86 people.
Earlier Saturday, militants destroyed a house once lived in by Pakistan's founder, Muhammad Ali Jinnah, who led the country to independence in 1947. The attack has huge significance in a country where Jinnah is so revered he's referred to as Quaid-e-Azam or the "great leader."
Attackers on motorcycles planted bombs at the 19th century residence in the mountain resort town of Ziarat, about 120 kilometers (75 miles) north of Quetta. Three of the bombs exploded and ignited a fire that destroyed the building, said senior police officer Asghar Ali Yousufzai.
The attackers also shot dead a police guard outside the residency, which had been turned into a museum.
Authorities said they were investigating reports that a Baluch Liberation Army flag had been hoisted at the residence. The militant group is one of the various factions fighting for independence from Pakistan.
"It's a symbolic attack on the idea of Pakistan," said Raza Rumi, director of the Islamabad-based Jinnah Institute.
UN Secretary-General Ban Ki-moon condemned the attacks in a statement, saying "no cause can justify such violence."
Saturday's violence serves as a huge challenge for Sharif and for the new chief minister of Baluchistan, Abdul Maalik Baloch.
Lashkar-e-Jhangvi is linked to al-Qaida and has been declared a foreign terrorist organization by the U.S., yet it operates with relative ease in Pakistan's populous Punjab province. The new Pakistani prime minister has been accused of being soft on militants using the province that his party has ruled for the last five years as a base.
Baloch's party was one of many that boycotted the 2008 provincial elections, but he and others decided to take part in the May 11 vote in an attempt to win change through the ballot box instead of through the violence favored by the separatists.
Ethnic Baluch separatists sought to derail the vote with a campaign of violence targeting their fellow Baluch, who the separatists view as traitors for taking part in the vote.
Many of the Baluch also view Pakistani security forces with deep distrust as a result of a repressive campaign against separatists by paramilitary soldiers and intelligence agents.