US President Joe Biden has vowed to keep up airstrikes against the extremist group whose suicide bombing at the Kabul airport killed scores of Afghans and 13 American service members. He warned another attack was “highly likely” and the State Department called the threat “specific” and “credible.” The Pentagon said the remaining contingent of US forces at the airport, now numbering fewer than 4,000, had begun their final withdrawal ahead of Biden"s deadline for ending the evacuation on Tuesday. After getting briefed on a US drone mission in eastern Afghanistan that the Pentagon said killed two members of the Daesh (so-called IS) group"s Afghanistan affiliate early Saturday, Biden said, “the extremists can expect more.” “This strike was not the last,” Biden said in a statement. “We will continue to hunt down any person involved in that heinous attack and make them pay.” The US Embassy in Kabul, Afghanistan warned Saturday evening of a "specific, credible" threat in the vicinity of Kabul airport, urging Americans to "leave the airport area immediately." "Due to a specific, credible threat, all US citizens in the vicinity of Kabul airport (HKIA), including the South (Airport Circle) gate, the new Ministry of the Interior, and the gate near the Panjshir Petrol station on the northwest side of the airport, should leave the airport area immediately," the Embassy said in a security alert. It stressed that US citizens "should avoid traveling to the airport and avoid all airport gates at this time." Earlier Saturday, Biden said in a statement that the situation on the ground in Afghanistan "continues to be extremely dangerous and the threat of terrorist attacks on the airport remains high." He added, "An attack is highly likely in the next 24-36 hours." Meanwhile, a White House official said that a total of about 2,000 people were evacuated from Kabul over 12 hours. Approximately 2,000 people were evacuated from Kabul between 3 a.m. and 3 p.m. ET Saturday, according to the White House. Eleven US military flights carried 1,400 people, while seven coalition flights evacuated 600, a White House official said. That compares to 4,200 people during the same period Friday. White House press secretary Jen Psaki told reporters Friday the number of evacuations would decrease amid the US military"s withdrawal mission. "Since Aug. 14, the US has evacuated and facilitated the evacuation of approximately 113,500 people. Since the end of July, we have re-located approximately 119,000 people," the official added. — Agencies