Afghan Taliban members announced on Monday the "defeat" of America and its allies, just one day after the U.S. and NATO formally ended their combat mission in the country, Reuters reported.

Now, the NATO-led International Security Assistance Force is launching a new two-year mission - Operation Resolute Support - which will see some 13,000 troops stay in the country and provide training and support to the Afghanistan military and police. An additional few thousand U.S. troops will stay to focus on counterterrorism, the BBC reported.

The Taliban viewed this as a decisive defeat, with spokesman Zabihullah Mujahid saying, "ISAF [the NATO-led International Security Assistance Force] rolled up its flag in an atmosphere of failure and disappointment without having achieved anything substantial or tangible," Reuters reported.

"We consider this step a clear indication of their defeat and disappointment," he added. "America, its invading allies ... along with all international arrogant organizations have been handed a clear-cut defeat in this lopsided war."

Mujahid said the Taliban, which ruled Afghanistan from 1996 to 2001 before being ousted by the U.S. and NATO over accusations they were harboring terrorists responsible for the Sept. 11, 2001 attacks, would continue to fight for "the establishment of a pure Islamic system" and "continue its Jihad and struggle so long as a single foreigner remains in Afghanistan in a military uniform."

The U.S. and its allies say the Afghan army and police have prevented the Taliban from taking significant territory, but this year has been the bloodiest since 2001, and attacks have increased as the Taliban continue to attempt to overthrow the government led by newly elected President Mohammad Ashraf Ghani.

According to the U.N., about 10,000 civilians have been wounded this year due to violence, and at least 4,600 members of the Afghan security forces have been killed, Bloomberg reported.

Since the beginning of the NATO mission in 2001, more than 3,500 foreign troops have been killed, including some 2,200 American troops, and at least 20,000 civilians have been killed.