KABUL -- Islamic State fighters captured some territory around Tora Bora, the former stronghold of Osama bin Laden in Afghanistan's eastern Nangarhar province, officials said Wednesday.

The push and capture of the giant cave complex that once housed the late al Qaeda chief would be a major scoop for the Islamic State group in its increasingly deadly rivalry with the Afghan Taliban. The caves had until now been under Taliban control.

Attahullah Khogyani, a spokesman in Nangarhar, said IS attacks in the mountain range began late on Tuesday night. Clashes continued into the day, with IS militants battling the Taliban and some local villagers in the area.

By Wednesday, the Islamic State group had managed to seize some territory around Tora Bora -- but not the bin Laden hideout itself, Khogyani said, adding that there were unspecified casualties on both sides.

"I can confirm that the ISIS fighters occupied some areas around Tora Bora, but not Tora Bora itself," said Khogyani, referring to the cave complex from where bin Laden and hundreds of other al Qaeda members escaped a massive U.S. bombing campaign in December 2001.

There has been no comment from ISIS or the Taliban so far.

However, Hazrat Ali, a lawmaker from Nangarhar confirmed that at least 12 Taliban fighters were killed in the battle with ISIS in Tora Bora. "Based on our information from local people, hundreds of ISIS fighters attacked Taliban militants in Tora Bora," said Ali.

He added that the Tora Bora mountain range, with the huge caves that once hid bin Laden, is strategically a very important location for the Islamic State group, giving it a remote and difficult to access location from where to launch attacks on both the Afghan government forces as well as the Taliban.

Shirin Agha Faqiri, a spokesman for the army crops in eastern Nangarhar, said ISIS fighters have captured much of the Tora Bora mountains, and even positioned some of their heavy artillery on the mountain peaks there.

"People and the local villagers are fleeing to other parts of the province," he added.

Tora Bora was bin Laden's last hideout in Afghanistan, where he and his al-Qaida followers where hosted by the Taliban. Only a few months after the Sep. 11, 2001 terror attacks, bin Laden escaped a U.S. assault in Tora Bora, and later managed to flee to Pakistan.

Bin Laden was killed in a U.S. Navy SEALs raid in May 2011 in the army garrison town of Abbotabad in neighbouring Pakistan, a raid that many Pakistanis have felt violated their country's sovereignty. Al Qaeda's No. 2 and bin Laden's deputy, Ayman al-Zawahri, took over the terror network.

The Taliban have continued their insurgency in Afghanistan and over the past two years, an affiliate of the Islamic State group which has been fighting in Iraq and Syria also emerged in Afghanistan, gaining a foothold in the country's east and clashing with the Taliban.

The United States estimates that there are about 600-800 ISIS fighters in Afghanistan, mostly in Nangarhar. The U.S. has concentrated on fighting them while also supporting Afghan forces against the Taliban.

In April, the U.S. used the biggest non-nuclear bomb ever dropped in combat by the American military against ISIS in Nangarhar, targeting a tunnel complex carved in the mountains that Afghan forces have tried to assault repeatedly but without success.