ISIS may be regaining strength just five months after it was ousted from its final stronghold in the Middle East, it has been claimed.
Islamic State fighters have been conducting guerrilla raids across Iraq and Syria as it attempts to recruit new members at allied-run camps, US intelligence officials say.
Sleeper cells have carried out sniper attacks, kidnappings and assassinations against security forces and other political leaders in recent months.
The terror group has around 18,000 fighters and has smuggled a $400m (£331m) war chest into neighbouring countries to help finance its fanatical religious war against the West, it is alleged.
ISIS once once boasted a brutal Islamic caliphate that controlled the fates of over 12 million people across Syria and Iraq, but saw its territory ebb away following a series of military losses against US-backed Iraqi forces.
Some 70,000 people remain in Syrian refugee camps which are filled with family members of ISIS fighters and there are fears that these camps could pose a future security risk.
U.S. Secretary of State Mike Pompeo acknowledged that Islamic State militants are gaining strength in some areas but said the group's capacity to conduct attacks has been greatly diminished.
"It's complicated. There are certainly places where ISIS is more powerful today than they were three or four years ago," Pompeo said in an interview with CBS This Morning.
But he said the group's self-proclaimed caliphate is gone and its attack capability has been made much more difficult.
Pompeo was asked about a New York Times report that the Islamic militant group was gaining new strength in Iraq and Syria.
President Donald Trump said in December that U.S. troops succeeded in their mission to defeat Islamic State in Syria and were no longer needed in the country. "We won," he said at the time.
Pompeo said the plan to defeat Islamic State in the region was executed with 80 other countries and was very successful.
However, he cautioned that there is always risk that there will be a resurgence of "radical Islamic terrorist groups," including al Qaeda and Islamic State.
In Geneva, a senior Chinese official warned on Tuesday that there was a danger of Islamic State militants re-emerging in Syria and called for progress in the political process between the Damascus government and the opposition to end the war.
China has long worried about ethnic Uighurs from China's far western region of Xinjiang who have traveled clandestinely to Syria and Iraq to fight with Islamist groups there.
Islamic State on Saturday in the Afghan capital of Kabul.
ISIS, in a statement on the messaging website Telegram, claimed responsibility saying its bomber had been able to infiltrate the reception and detonate his explosives in the crowd of "infidels".
The attack came as the Taliban and the United States are trying to negotiate an agreement on the withdrawal of U.S. forces in exchange for a Taliban commitment on security and peace talks with Afghanistan's U.S.-backed government.
