The travel warning comes after severe attacks in both France and Mali, and following a manhunt for suspects in the former incident in Belgium. Armed assaults at cafes, a sports stadium, and a concert venue in Paris on November 13 left 130 people dead . The Islamic State group, also known as ISIS or Daesh, later claimed responsibility for the attacks.One American was killed when fighters from a group linked to al-Qaida stormed the Radisson hotel in Mali and took more than 170 people hostage. The militant Islamist group Mourabitounes, which split from al-Qaida's North Africa branch several years ago, has claimed responsibility for the attack, the AP reported.Belgium has extended its maximum-security alert in Brussels , though schools and the city's metro system could reopen on Wednesday, Reuters reports. Brussels has been on alert since French authorities revealed that two of the Paris attackers lived in Belgium. Authorities in France and Belgium are also searching for Salah Abdeslam, one of the suspected attackers, who is believed to have returned to Brussels after the attacks.In the travel advisory, U.S. officials warn that terrorist groups and individuals could be planning further attacks this holiday season. "Current information suggests that ISIL (aka Daesh), al-Qaida, Boko Haram, and other terrorist groups continue to plan terrorist attacks in multiple regions," the warning stated. The advisory notes that in the past year, there have been terrorist attacks in Nigeria, Denmark, and Turkey as well.The State Department notes that travelers should be prepared for any additional security screenings they might encounter, and recommends that they "stay in touch with family members and ensure they know how to reach you in the event of an emergency."