The world-wide terror threat is evolving as Al-Qaeda linked groups and other militants become increasingly violent and a new generation of global terrorists is spawned in Syria, the US warned Wednesday.
US counter-terrorism efforts focused on Al-Qaeda have "degraded" the core leadership, but "subsequently 2013 saw the rise of increasingly aggressive and autonomous AQ affiliates and like-minded groups in the Middle East and Africa."
Even Al-Qaeda leader Ayman al-Zawahiri, who took over after Osama bin Laden was killed in a US operation in 2011, has had "difficulty in maintaining influence," said the State Department's 2013 Country Reports on Terrorism.
"The terrorist threat continued to evolve rapidly in 2013, with an increasing number of groups around the world -- including both AQ affiliates and other terrorist organizations -- posing a threat to the United States, our allies, and our interests."
The civil war in Syria has proved a fertile breeding ground attracting thousands of foreign fighters who have joined the fight against President Bashar al-Assad.
They seized advantage of the chaos and lack of governance as well as a flow of money from the Gulf for Sunni terror groups, particularly those operating in Syria.
But Assad has also been aided by Shiite militia, such as the Lebanon-based Hezbollah, funded and supported by Iran adding to the violence on the ground.
Many governments are "becoming increasingly concerned that individuals with violent extremist ties and battlefield experience will return to their home countries or elsewhere to commit terrorist acts," the report noted.
This has fuelled growing "concern about the creation of a new generation of globally-committed terrorists, similar to what resulted from the influx of violent extremists to Afghanistan in the 1980s."
Extremist violence last year was also increasingly marked by "sectarian motives," which the US said was a "worrisome trend."
Africa also "experienced significant levels of terrorist activity" last year, the report said, fingering the Somalia-based Shebab, which was behind September's Nairobi mall attack, as the continent's main threat.
"Driven out of major urban areas, Shebab has returned to a strategy focused on asymmetric attacks intended to discredit and destabilize the nascent federal government of Somalia," the report said.
But it highlighted successful efforts by French and allied African forces to push back Al-Qaeda in the Islamic Maghreb and other extremist groups in northern Mali.
And it noted that the number of rocket attacks launched on Israel by Hamas militants from the Gaza Strip and Sinai peninsula was the lowest in more than a decade.
Just 74 rockets were launched in 2012 compared to 2,557 the year before, of which Israeli authorities said only 36 actually hit southern Israel.