KABUL (Reuters) - A suicide attacker rammed a car full of explosives into a bus leaving Afghanistan’s top military training center in Kabul on Saturday, killing at least 15 soldiers, including cadets and their trainers, officials said.

Taliban insurgents claimed responsibility for the attack, the latest in a particularly deadly week for Afghanistan’s security forces.

The bombing was also the second major attack in the capital Kabul in 24 hours after a suicide attack at a Shi’ite mosque killed more than 50 worshippers on Friday night.

“Army personnel were coming out of Marshal Fahim University when a suicide bomber in a car targeted them. Fifteen soldiers who were there for training were killed and four others were wounded,” Ministry of Defence spokesman Dawlat Wazari said.

A statement from President Ashraf Ghani’s office said the bus was carrying trainers and cadets from the defense university on the western outskirts of Kabul that is home to the Afghan military’s officer training school and other military academies.

Afghan security forces have been struggling against the Taliban since most foreign troops left at the end of 2014.

U.S. President Donald Trump committed to an open-ended military training and support mission in Afghanistan in August, despite criticism that it is no closer to peace despite billions of dollars in aid and nearly 16 years of U.S. and allied operations.

Taliban spokesman Zabihullah Mujahid claimed responsibility for Saturday’s car bomb in an email to reporters.

The Taliban have been waging an insurgency for a decade and a half in an attempt to overthrow the Western-backed government in Kabul and re-establish a fundamentalist Islamist regime.

The insurgents now control or contest about 40 percent of Afghanistan.

HEAVY AFGHAN TOLL

Afghan security forces including police were being killed at a rate of about 600 per month in battles and targeted bombings earlier this year, according to a U.S. report.

This week’s toll looked to be particularly heavy for Afghan forces after attacks across the country, including Taliban fighters using captured U.S.-provided Humvee vehicles as vehicle bombs to ram into fortified compounds.

On Thursday the Taliban stormed a military base in the southern province of Kandahar, killing at least 43 of the 60 soldiers manning the base, which was left in ruins.

Two days earlier dozens of security personnel were killed and scores wounded in Taliban attacks on government compounds in Paktia and Ghazni provinces, with a senior provincial police commander among the dead.

In addition to the Taliban, Afghanistan has in recent years seen a rise in violence claimed by fighters who have claimed loyalty to the Islamic State’s Middle East-based leadership, although the movement controls little territory in Afghanistan.

Islamic State claimed responsibility for a suicide attack in Kabul on Friday evening in which a bomber walked into a Shi’ite Muslim mosque as people were praying and detonated his explosives.

The toll in the attack on Imam Zaman mosque rose to 54 killed, including children, and 55 wounded, a deputy minister for religious affairs, Dai-ul Haq Abid told a news conference on Saturday.

Another mosque attack on Friday killed at least 33 people in central Ghor province.