The US has strongly condemned the deadly suicide bombing at a mosque in Pakistan's Peshawar city on Monday, saying "terrorism is indefensible," and to "target worshippers is unconscionable." The death toll from the suicide attack rose to 100 on Tuesday after rescue workers retrieved more bodies from the debris of the devastated mosque inside a major police facility in Peshawar, capital of the restive Khyber Pakhtunkhwa province.

According to Pakistani security officials, the suicide bomber who was present in the front row during the Zuhr (afternoon) prayers on Monday blew himself up, causing the roof to collapse on the worshippers -- one of Pakistan's deadliest attacks in recent years.

“The United States strongly condemns the terrorist attack on a mosque in Peshawar, Pakistan with reports today that the death toll has now risen to 100 people,” Andrienne Watson, spokesperson of the National Security Council, White House said on Tuesday.

“This is tragic and heartbreaking news, and we extend our deep condolences to the loved ones of those who have lost their lives. Terrorism is indefensible, and to target worshippers is unconscionable,” Watson said.

Washington stands ready to provide support to Pakistan in its efforts to recover, he added.

"Devastating news in Pakistan, where over 100 were killed by a suicide bomb at a mosque and another 40 people died in a bus crash," tweeted Senator Bob Casey.

“My condolences are with the Pakistani people as they mourn the loss of life,” he added.

The Tehreek-e-Taliban Pakistan (TTP), known as the Pakistani Taliban, claimed responsibility for the suicide attack, saying it was part of a revenge attack for slain TTP commander Umar Khalid Khurasani who was killed in Afghanistan in August last year.

The TTP, set up as an umbrella group of several militant outfits in 2007, called off a ceasefire with the federal government and ordered its militants to stage terrorist attacks across the country.

The group, which is believed to be close to al-Qaeda, has been blamed for several deadly attacks across Pakistan, including an attack on army headquarters in 2009, assaults on military bases, and the 2008 bombing of the Marriott Hotel in Islamabad.

In 2014, the Pakistani Taliban stormed the Army Public School (APS) in the northwestern city of Peshawar, killing at least 150 people, including 131 students.

The attack has sent shockwaves across the world and was widely condemned.

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