Afghanistan's U.N. ambassador says a new offensive against the government and the Afghan people is compounded by an unprecedented convergence of Taliban insurgents, more than 7,000 foreign fighters and violent groups including the Islamic State.

Zahir Tanin told the U.N. Security Council Monday that these groups not only target Afghan troops and civilians with suicide bombings, improvised explosives, hostage-taking and assassinations but they seek control of districts and provinces as bases for their activities in Afghanistan as well as south and central Asia.

Nicholas Haysom, the U.N. envoy for Afghanistan, said Afghanistan is meeting its security challenges "but it is nonetheless being increasingly tested."

Afghan forces "have been undeniably stretched as they take on full security responsibilities" following the end of the U.S. and NATO combat mission, he said.