QUETTA, Pakistan (AP) — An hours-long attack by a group of militants, including suicide bombers who stormed a Pakistani police academy in the southwestern city of Quetta, left at least 48 dead, mostly police trainees, officials said Tuesday.

No one immediately claimed responsibility for the attack, for which authorities blamed the Taliban and al-Qaida-linked groups. Pakistani troops responding to the assault said they killed one of the suicide bombers while two others detonated their explosives vests, blowing themselves up.

Health officials said over 116 have been wounded — mostly police recruits and some paramilitary troops. Noorul Haq, top health official in Quetta, the capital of the country's restive Baluchistan province, said several of the wounded were in critical condition, sparking concerns the death toll would rise further.

A security official, speaking on condition of anonymity because he was not authorized to talk to the media, put the death toll at 51 but that figure could not independently be confirmed.

The attack started at 11:30 p.m. on Monday and provincial Home Minister Sarfraz Bugti said the attackers shot and killed a police guard at the watch tower before they stormed into the facility.

There were disparate figures as to the number of attackers. Provincial police chief Ahsan Mahboob said there were four gunmen while a statement issued by the military put the number of attackers at up to six.

About 700 cadets, trainees, instructors and other staff were inside the academy when it was attacked, Bugti said, adding that the gunbattle with the militants lasted for at least four hours.

Once inside the academy grounds, Pakistani media said the gunmen headed straight to the dorms housing the cadets and trainees and opened fire, shooting indiscriminately. Some of the cadets jumped off the rooftops and through windows to try to escape.

"They were rushing toward our building, firing," one cadet told Pakistani Geo TV news channel. "We rushed for safety toward the roof and jumped down in the back of the building."

Another recruit, his face covered in blood, told the station the gunmen shot at whoever they saw. "I ran away, just praying God might save me," he said.

After hours of siege, the attack was over, said the home minister, Bugti. Pakistani forces tightened security around the academy and Quetta hospitals were the wounded were taken.

Footage aired on local television stations showed ambulances rushing out of the main entrance of the academy as fire engines struggled to put out fires set off by the explosions from the attackers' suicide vests. Most of those being treated at the city hospitals had gunshot wounds, although some sustained injuries jumping off the rooftop of the hostel housing the cadets to escape the gunmen.

"This war isn't over," said Pakistani Interior Minister Chaudhry Nisar Ali Khan. "The enemy is weakened, but not eliminated."

Maj. Gen. Sher Afgan, head of the Pakistani paramilitary force which is primarily responsible for the province, claimed the attackers had received instructions from commanders in neighboring Afghanistan. He said they were most likely from the banned Lashker-e-Jhangvi Al-Almi militant group affiliated with al-Qaida and the Taliban. The Sunni militant group has mainly targeted minority Shiite Muslims whom its members consider to be infidels.

But neither Lashker-a-Jhangvi nor any other militant group, including the breakaway Pakistani Taliban faction of Jamaat-ul Ahrar, which has staged several large attacks previously in Baluchistan, claimed responsibility for the assault on the police academy.

Though Jamaat-ul Ahrar has not formally pledged allegiance to Islamic State group, it says it supports the cause of the Sunni extremist group fighting mainly in Syria and Iraq.

Afghanistan condemned the attack in Quetta and dismissed Pakistan's allegations that the assault was planned from bases inside Afghanistan.

"Afghanistan is the biggest victim of terrorism and denounces all terrorist attacks," said Mohammad Haroon Chakhansuri, spokesman for Afghan President Ashraf Ghani.

In a separate statement, Ghani also condemned the attack, saying that "terrorism is a threat throughout the region, which is reflected in the brutal act today in Quetta."

Pakistan maintains that militants fleeing army operations in the tribal regions regularly escape across the border, finding safe havens inside Afghanistan. For his part, Ghani has been deeply critical of Pakistan, saying it has provided safe havens to the Taliban and in particular the violent Haqqani network.

For over a decade, Baluchistan has been the scene of a low-intensity insurgency by nationalist and separatist groups demanding a bigger share in the regional resources. Islamic militants and Sunni sectarian also have a presence in the province.

Pakistan has carried out several military operations against militants in country's lawless tribal regions along Afghanistan border, including a major push that started mid 2014 in North Waziristan, a militant base. The Islamic militants have killed tens of thousands of people in their bid to overthrow Pakistan's government and install their own harsh brand of Islamic law.

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Associated Press Writers Zarar Khan and Asif Shahzad in Islamabad; Riaz Khan in Peshawar; Ishtiaq Mahsud in Dera Ismail Khan, Pakistan, and Amir Shah in Kabul, Afghanistan contributed to this report.