US Vice President Joe Biden described the Kurdistan Workers Party (PKK) as a terror group "plain and simple" during a joint news conference with Turkish Prime Minister Ahmet Davutoglu in Istanbul on Saturday, suggesting that the militant group poses as much of a threat to Turkish national security as the Islamic State (IS).

"IS is not the only existential threat to the people of Turkey, the PKK is equally a threat and we are aware of that," Biden said. "What they continue to do is absolutely outrageous."

The armed Patriotic Revolutionary Youth Movement (YDG-H), the youth wing of the PKK, has been ramping up fighting in southeast Turkey since ceasefire negotiations fell apart in July 2015. The YDG-H has clashed violently with Turkish government forces, who have responded to the insurgency with sniper fire and artillery.

Cellphone video footage and pictures emerging from the region, where journalists are banned from visiting, portray a grim scene, where heavy fighting has devastated civilian areas and killed scores of people. At least 150 residents have been reported killed in less than a year, including women, young children, and the elderly.

Meanwhile, a recent report by Amnesty International said the Turkish government's imposition of round-the-clock curfews and severing of public services is "putting the lives of up to 200,000 people at risk and amounts to collective punishment."

"In some areas, crippling curfews that don't allow people to leave their houses at all have been in place for more than a month," wrote John Dalhuisen, Amnesty International's director for Europe and Central Asia.

The divisive impact that the conflict is having on the rest of the country was highlighted in the circulation of two recent petitions by Turkish academics. The first, which received 1,128 signatures, accused the Turkish state of massacring civilians and children in their counter-PKK operations. In rebuttal, nearly 6,000 other academics signed a petition under the name "Academics against Terror," expressing solidarity with the Turkish fight in the southeast and contending that government forces have acted within the law.

Watch the VICE News dispatch Pushing Back the Islamic State: The Battle for Rojava:

At Saturday's press conference, Biden stressed the continuing strategic alliance between Turkey and the US. Biden's condemnation of the PKK was significant because it appeared to be an attempt to assuage Turkish concerns that Washington might lend additional support to the PKK and other Kurdish militias fighting against IS.

The Kurds have been one of the most effective fighting forces against IS, recapturing territory in northern Syria and also pushing the militants back in northern Iraq. The US recently opened an air base in the Kurdish city of Erbil in northern Iraq, which will reportedly be used for surveillance operations.

Amnesty has also accused Kurdish peshmerga forces in northern Iraq of razing thousands of homes in Arab communities in revenge for their perceived support of IS. "The forced displacement of civilians and the deliberate destruction of homes and property without military justification, may amount to war crimes," said Donatella Rovera, Amnesty International's senior crisis response advisor, who carried out the field research in northern Iraq.

Biden praised Turkey for taking "very important steps to improve the security of its border" from IS militants, and said that the two nations were increasingly seeing eye to eye on the strategy underlying their "shared mission on the extermination of IS."

The vice president met with Turkish President Recep Tayyip Erdogan later on his visit.