"The Afghanistan-Pakistan border region remains a sanctuary for various groups, including al Qaeda, the Haqqani Network, Lashkar-e Tayyiba, Tehrik-e-Taliban Pakistan, the Islamic State of Iraq and the Levant - Khorasan Province, and the Islamic Movement of Uzbekistan," the Pentagon said in its six-monthly report to the Congress on Afghanistan.
"These extremist sanctuaries remain a security challenge for both Afghanistan and Pakistan and pose a threat to regional stability," said the report which covers the period from June 1 to November 30.
Observing that the Afghan government's relationship with Pakistan remains a critical aspect of enhancing security and stability in the country, the report said since the beginning of President Ashraf Ghani's tenure, leaders from both countries have made a concerted effort to improve relations and better address mutual security interests.
In their first fighting season against an Afghan-led counterinsurgency, the Taliban-led insurgent threat remains resilient, the report said, adding that the increase in violence over the reporting period, and the fighting season overall, when compared to last year was reflected in public perceptions of security as well.
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"In the second half of 2015, the overall security situation in Afghanistan deteriorated with an increase in effective insurgent attacks and higher ANDSF and Taliban casualties," the Pentagon said.
Though the insurgency remains resilient, the Afghan government remains in control of all major population centers and continues to deny the Taliban strategic ground throughout the country, it said.
The Taliban have remained active in their traditional strongholds, namely in Helmand in the south and Logar and Wardak in the east, and also created a sense of instability for brief periods of time in other parts of the country, such as in Kunduz in northern Afghanistan, the Pentagon said.
The ANDSF consistently retook ground they had temporarily lost to the Taliban.