An explosion tore through a public park crowded with families in the Pakistani city of Lahore Sunday night, killing as many as 65 people and wounding more than 200, according to Pakistani officials.

The blast occurred around 6:30 p.m. local time in a parking lot at Gulshan-e-Iqbal Park, near a children’s ride. Gulshan-e-Iqbal is one of the largest parks in Lahore, the capital city of the Punjab province, Pakistan’s most populous province. Many were there to celebrate the Easter holiday.

The exact number of victims is not yet known. News outlets report there may be between 50 and 70 fatalities, and as many as 300 injured. Most of the injured were women and children, according to the AFP. Officials fear the number of dead may rise as many of the wounded were in critical condition.

The attack appeared to be a suicide bombing. A faction of the militant Taliban group in Pakistan, known as Jamaat-ul-Ahrar, has claimed responsibility for the attack, saying it had deliberately targeted Christians, the AP reported. The group warned more would follow.

Photos from the scene showed rescue workers evacuating injured people from the park. Blankets covered the bodies of the dead, which were carried away on gurneys.

Dozens of ambulances were dispatched to the scene, according to Pakistani news outlets. Army troops were also called to the site. The Punjab government placed local hospitals in a state of emergency and ordered all public parks to be closed.

Hundreds of citizens went to hospitals to donate blood to the victims of the attack, Reuters reported. Careem, a mobile app-based car service that operates in Pakistan, said it was offering free rides to those seeking to donate blood. Facebook activated its safety-check feature in Lahore, allowing users near the attack to notify friends and family about their safety.

The Punjab government has announced three days of mourning for the province.

Shehbaz Sharif, the chief minister of the Punjab province, condemned the terrorist attack. Daniyal Hassan, a reporter with the Pakistani channel Dawn News, tweeted a video of Sharif donating blood at a hospital.

“Those who targeted innocent citizens do not deserve to be called humans,” Sharif said in a statement posted on Twitter. “They are beast [sic]... We will come after you.. We will hunt you down.”

Pakistan’s Chief of Army Staff General Raheel Sharif convened a meeting with high-level military officials to discuss security following the attack, said General Asim Bajwa, the director-general of the ISPR, the public-relations department of the Pakistani military. Officials “resolved that we must bring the killers of our innocent brothers, sisters and children to justice,” Bajwa said on Twitter.

Hasan Imran, a resident who had gone to Gulshan-e-Iqbal Park for a walk, told Reuters that “when the blast occurred, the flames were so high they reached above the trees and I saw bodies flying in the air.”

Javed Ali, who lives across from the park, described the attack to AFP, saying the force of the explosion shattered the windows of his home:

“Everything was shaking, there were cries and dust everywhere.

“After ten minutes I went outside. There was human flesh on the walls of our house. People were crying, I could hear ambulances.”

He added: “It was overcrowded because of Easter, there were a lot of Christians there. It was so crowded I told my family not to go.”

The United States, an ally of Pakistan, called the attack a “cowardly act.” “Together [with Pakistan] we will be unyielding in our efforts to root out the scourge of terrorism,” National Security Council spokesman Ned Price said in a statement Sunday.

The government of Pakistan has battled an Islamist insurgency for over a decade. Militant groups, including the Pakistani Taliban, routinely carry out attacks in the country, targeting public places, government and military buildings, and transportation. Lahore, located on the country’s eastern border with India, had largely escaped the violence in recent years. In 2010, suicide attacks in the city killed 139 people in separate incidents in two months.