A man identified as Suleiman Abu Ghaith appears in this still image taken from an undated video address
In a global advisory issued to its citizens, the US has asked them to maintain a high level of vigilance and take appropriate steps to increase their security awareness.
The advisory includes South Asia, and India in particular, among other places around the world.
India has experienced terrorist and insurgent activities that may affect US citizens directly or indirectly, the State Department said.
Anti-Western terrorist groups, some of which are on the US government's list of designated Foreign Terrorist Organizations, have been active in India, including Islamist extremist groups such as Harkat-ul-Jihad-i-Islami, Harakat ul-Mujahidin, Indian Mujahideen, Jaish-e-Mohammed, and the Pakistan-based Lashkar-e Tayyiba, it said.
Terrorists have targeted public places in India frequented by westerners, including luxury and other hotels, trains, train stations, markets, cinemas, mosques, and restaurants in large urban areas, it said.
The US government, it said, continues to receive information that terrorist groups in South Asia may also be planning attacks in the region, possibly against US government facilities, US citizens, or US interests.
Kidnappings and hostage incidents involving US citizens have become increasingly prevalent as al-Qaeda and its affiliates have increased attempts to finance their operations through kidnapping for ransom operations, it said.
Al-Qaeda in the Arabian Peninsula (AQAP) and al-Qaeda in the Islamic Maghreb (AQIM) are particularly effective with kidnapping for ransom and are using ransom money to fund the range of their activities.
"Current information suggests that al-Qaeda, its affiliated organizations, and other terrorist groups continue to plan and encourage kidnappings of US citizens and Westerners.
"US citizens should closely monitor Travel Warnings and Alerts, as well as Country Specific Information, on the Department of State's travel website to review the latest safety and security information for destination countries," the State Department said.