A suicide bomber claimed the lives of at least 65 people who were celebrating Easter weekend at a crowded children's park in Pakistan Sunday, officials said.

The explosion, which also injured more than 300 others, took place in the parking area of Gulshan e-Iqbal Park and targeted Christians celebrating the holiday in Lahore, the capital of the Punjab province. Witnesses claimed to have seen body parts laying across the parking lot after the dust settled.

"When the blast occurred, the flames were so high they reach above the trees and I saw bodies flying in the air," said Hasan Imran, a 30-year-old resident who had gone to the park for a walk.

Lahore Police Chief Dr. Haider Ashraf said that most of the victims who were killed and injured in the blast were women and children.

Tehreek-e-Taliban Pakistan Jamaatul Ahrar (TTP-JA), a Pakistani Taliban splinter group headed by Maulvi Omar Khalid Khurasani, has claimed responsibility for the attack.

"Members of the Christian community who were celebrating Easter today were our prime target," TTP-JA spokesman Ehsanullah Ehsan told NBC News from an undisclosed location with an Afghan cell number.

Ehsan added that this was the first in a series of attacks that were planned this year in different parts of Pakistan. He also said that women and children were not on their list of targets and that the group's main targets were male members of the Christian community.

Ashraf said that police guards and private security guards have manned the park. "We are in a warlike situation and there is always a general threat, but no specific threat alert was received for this place," he added.

Salman Rafique, a health adviser for the Punjab provincial government, said that most of the wounded were sent to hospitals and were undergoing emergency surgery, adding that the death toll is expected to increase.

"We were just here to have a nice evening and enjoy the weather," Nasreen Bibi, who was waiting for doctors to update her on the condition of her 2-year-old injured daughter, said at the Services Hospital. "May God shower his wrath upon these attackers. What kind of people target little children in a park?"

The Punjab government has since ordered all public parks to be closed and announcement three days of mourning in the province. The U.S., a strategic ally of Pakistan, condemned the attack, with National Security Council spokesperson Ned Price calling it a "cowardly act."

"We send our deepest condolences to the loved ones of those killed, just as our thoughts and prayers are with the many injured in the explosion," Price added.

"The United States stands with the people and government of Pakistan at this difficult hour. We will continue to work with our partners in Pakistan and across the region ... to root out the scourge of terrorism."

The explosion follows less than a week after the terrorist attack at a Brussels airport and subway station, which killed 31 and injured 270. ISIS claimed responsibility for the attack.