The report by the US National Counterterrorism Centre, an arm of the Central Intelligence Agency, said 1,907 people died in 651 terrorist attacks in 2004, a tripling of the previous year’s figures.
In 2003, there were 208 attacks causing 625 deaths, according to State Department figures released last year.
State Department Counselor Philip Zelikow said: “I think we are winning the war on terror but it is a very long struggle.”
“And I want to triple underscore: No complacency.”
The NCTC report is the first time the figures were released, and is separate to an annual State Department country report on terrorism, which said the global threat remains “significant”, with Iraq remaining the central battleground.
More than half the attacks reported by the NCTC for 2004 were in South Asia, which recorded 327 incidents that produced 502 deaths.
Most of the incidents were reported in the divided Kashmir region, claimed by both India and Pakistan.
Most of the deaths were in the Middle East, with a reported 726 deaths in 270 attacks.
But the bloodiest strikes were in Europe and Eurasia, where 636 people died in 24 incidents, including the Madrid train bombing and the Beslan school siege in Russia.
The State Department’s annual Country Reports on Terrorism 2004 identified al-Qaeda as the main threat, with Cuba, North Korea, Syria and mostly Iran as continued supporters of terrorism.
“The United States and other donor nations must intensify to bolster the political will and the intelligence, law enforcement, financial and military capabilities of partner nations to combat terrorism, on their own or with us,” said the report.
Earlier this month, the department said it had decided not to publish statistics after widely publicised errors were found in figures for 2003 that had to be revised.
NCTC acting director John Brennan said the centre has used new methods and criteria to establish the fresh statistics, and said it is not accurate to compare 2004 figures with previous years.
“An increased level of effort allowed a much deeper review of far more information and along with Iraq were the primary reasons for the significant growth in terrorist incidents being reported,” he said.