Jamat-ul-Ahrar, a splinter group of Pakistan's Tehreek-i Taliban (TTP) -- also known as the Pakistani Taliban -- claimed responsibility for the attack in a statement emailed to CNN.

Monday's blast occurred at Charing Cross in Lahore, the capital of Pakistan's Punjab province and the second-largest city in the country.

Pakistani Prime Minister Muhammad Nawaz Sharif strongly condemned the blast, according to a statement obtained by CNN, saying that "such cowardly acts cannot deter the resolve of the nation to stand against terrorism and our government is committed to root out this menace."

Journalist Adeel Raja and CNN's Sophia Saifi reported from Islamabad, with CNN's Eric Levenson writing and reporting from New York. Journalists Zahir Shah and Saleem Mehsud also contributed to this report.