KANDAHAR, Afghanistan -- A suicide bomber struck a NATO convoy near the southern Afghan city of Kandahar on Wednesday killing two U.S. service members, the Pentagon said.

The Taliban promptly took responsibility for the attack, and a spokesman for the insurgents said the bombing allegedly killed 15 soldiers - a claim that appeared exaggerated as many similar Taliban claims have been in the past.

Navy Capt. Jeff Davis, a Pentagon spokesman, said two U.S. service members were killed in action in the attack and that more information would be provided when it became available.

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In their claim of responsibility, the Taliban also said the attack destroyed two armored tanks. The insurgents' spokesman for southern Afghanistan, Qari Yusuf Ahmadi, said fighter Asadullah Kandahari was the "hero" who carried out the attack with a small pick-up truck, packed with explosives.

U.S. troops assess the damage to an armored NATO vehicle after a Taliban suicide attack in Kandahar province, Afghanistan, Aug. 2, 2017. Reuters/Ahmad Nadeem

Kandahar province was the Taliban spiritual heartland and the headquarters of their leadership during the five-year rule of the Taliban, which ended with the U.S. invasion in 2001.

Eyewitness Ghulam Ali, who runs a mechanics shop near the attack site on the outskirts of the city of Kandahar, said the intensity of the blast knocked him out.

When he came to, he saw a military vehicle on fire on the road. He stepped out of his shop but a sudden burst of gunfire drove him back inside, he said. Then, helicopters arrived and he saw soldiers being taken away from the scene but could not determine the extent of their injuries.

Shah Agha Popal, who runs a vehicle parts shop also nearby, said he also saw soldiers being taken away by two helicopters.

"But I couldn't tell if they were wounded or if they were dead," he said.

The combined U.S. and NATO troop contingent currently in Afghanistan is about 13,500. The Trump administration is deciding whether to send about 4,000 or more U.S. soldiers to Afghanistan in an attempt to stem Taliban gains.

The attack came as Afghan authorities in western Herat province tightened security ahead of a mass funeral for the victims there of an attack the previous evening that killed 32, said provincial governor's spokesman Jilani Farhad.

Another 66 worshippers were injured in the horrific suicide assault Tuesday evening. As worshippers began their evening prayers a suicide attacker sprayed bullets at the private guards protecting the mosque before entering inside and detonating his explosives.

The Islamic State of Iraq and Syria, or ISIS, claimed responsibility for the mosque bombing saying it was carried out by two of its fighters. ISIS said in a statement that the two men, whom it identified as Amir Qassim and Tayeb al-Kharasani, also used automatic rifles in the Shiite mosque before they detonated themselves.

The statement claimed that the attack killed nearly 50 and wounded more than 80.

Witnesses said demonstrators brought 31 bodies near the provincial governor's residence in a large freezer truck. Protesters demanded the people behind the brutal assault be arrested.

On Monday, after taking credit for an attack on the Iraq Embassy in the heart of the Afghan capital Kabul, the ISIS affiliate in Afghanistan warned it would strike Shiites. The Sunni militant group considers Shiite Muslims as apostates.

Also on Wednesday the Taliban ambushed and killed Jaghatu District Gov. Manzur Hussain and a passenger in his car, Ghazni provincial police chief Mohammad Mustafa Mayar said.

The Taliban have stepped up their attacks in recent weeks hitting district headquarters, government officials and Afghan National Security Forces with increasing frequency.