— As many as four suicide bombers stormed a mosque in northwestern Pakistan during Friday prayers, killing at least 19 people and wounding dozens of others in another major attack targeting the country’s Shiite minority.

In a statement, the Pakistani Taliban asserted responsibility. A Taliban spokesman said the attack was a response to Pakistan’s resumption of executions after a six-year moratorium. Over the past two months, about 22 people imprisoned on terrorism counts have been hanged.

Friday’s bombing was the first major security breach in the city of Peshawar since the Pakistani Taliban massacred about 150 students and teachers at an army-run school in December in one of the worst terrorist attacks in the country’s history.

Police officials said Friday’s attack began about 1 p.m. when assailants entered the Shiite mosque from an adjoining building. They were quickly stopped by security guards. But at least one of them — and possibly all four — were fitted with suicide vests and blew themselves up, officials said.

Imran Ahmad, who had been inside the mosque, said he heard three explosions as Friday prayers were ending. But he and other witnesses said it appeared that at least two of the explosions were caused by hand grenades.

The Pakistani military responded to the December school attack by stepping up raids on militant havens along the country’s border with Afghanistan. Paramilitary forces also have targeted hundreds of homes and businesses, rounding up more than 5,000 people suspected of militant activity.

Although the overall number of terrorist attacks in Pakistan has declined over the past year, the country’s Shiite population continues to endure some of the most brutal violence. Sunni-led militant factions such as the Taliban consider Shiites to be heretics.

About three-fourths of Pakistanis are Sunni Muslims, while Shiite Muslims make up 15 to 20 percent of the population.

Many Shiites have been killed in bombings targeting mosques and markets as well as buses transporting pilgrims to religious observances in neighboring Iran, which is majority Shiite. But in recent years, a wave of assassinations also has targeted Shiite doctors, lawyers and other professionals in Karachi and other major cities.

In a statement Friday after the mosque attack, Pakistani Prime Minister Nawaz Sharif said his government is “committed to eradicating the menace of terrorism and extremism from the country.”

Haq Nawaz Khan in Peshawar contributed to this report.