The nation’s spy chief called on former intelligence contractor Edward Snowden to return a massive trove of classified documents on Wednesday during a congressional hearing on security threats that was dominated by heated exchanges over that security breach and the surveillance programs subsequently exposed.

Speaking before a Senate panel, James R. Clapper Jr. outlined an array of dangers to American interests, including a rise in cyberthreats and the emergence of Syria as a magnet for Islamist militants linked to al-Qaeda.

But after skimming through those developments, Clapper focused his opening remarks on Snowden, delivering a blistering stream of criticism in which he described the former contractor for the National Security Agency as a hypocrite who has severely undermined U.S. security.

Clapper said the documents exposed by Snowden have bolstered adversaries, caused allies to curtail cooperation with the United States, enabled terrorist groups to alter the ways they communicate, and put lives of U.S. intelligence operatives at risk.

“Snowden claims that he has won and that his mission is accomplished,” Clapper said. “If that is so, I call on him and his accomplices to facilitate the return of the remaining stolen documents that have not yet been exposed to prevent even more damage to U.S. security.”

Clapper did not clarify what he meant by “accomplices,” or whether he was referring to journalists who have received documents from Snowden. A spokesman said Clapper was “referring to anyone who is assisting Edward Snowden to further threaten our national security through the unauthorized disclosure of stolen documents related to lawful foreign intelligence collection programs.”

There were a number of sharply worded exchanges during the annual worldwide threat hearing - an ordinarily sober discussion - turning it into a platform for U.S. intelligence officials and some of their critics in Congress to vent months of pent-up frustration with the Snowden fall-out.

At one point, Sen. Ron Wyden (D-Ore.) decried what he described as a “culture of misinformation” among U.S. intelligence officials, cataloguing misstatements and falsehoods that had been exposed by Snowden.

Trust in those agencies “has been seriously undermined by senior officials’ reckless reliance on secret interpretations of the law and battered by years of misleading and deceptive statements,” Wyden said.

Among the most pointed examples was Clapper’s testimony before the same committee last year that U.S. spy agencies did not gather data on millions of Americans. Months later, Snowden’s disclosures showed that the NSA had secretly compiled a database containing the phone records of nearly every American.

The recriminations over Snowden come as President Obama has pledged to end the NSA’s collection of such records and underscored the extent to which Snowden-related damage control has been a major distraction for spy agencies struggling to keep up with rapidly shifting security threats.

U.S. officials on Wednesday warned that political turmoil in the Middle East was accelerating the atomization of the al-Qaeda terrorist network, with offshoots gaining strength in Syria, Yemen, Iraq and Egypt.

Clapper said that Syria has attracted about 7,000 fighters from as many as 50 nations beyond its borders, including a steady flow from the Middle East and Europe. The trend has alarmed counterterrorism officials, raising concern that militants trained and indoctrinated in Syria might use their Western passports to carry out attacks against the United States or its allies.

Syria is “in some respects a new FATA,” Clapper said, referring to the tribal belt of Pakistan where al-Qaeda has been based for more than a decade. One of the leading militant groups in Syria, known as Jabhat al-Nusra, “does have aspirations for attacks on the homeland.”

His concern was echoed by senior lawmakers, including Sen. Dianne Feinstein (D-Calif.), the chairman of the Senate Intelligence Committee, who noted that the friction among Islamist groups in Syria has become “so dire that even al-Qaeda’s central leader . . . has denounced the activities of one group as too extreme to countenance.”

A spike in violence in Iraq has brought the number of attacks there to levels not seen since U.S. forces left in 2011, U.S. officials said.

They also warned of a spike in threat reporting associated with the upcoming Olympic Games in Sochi, Russia. Citing extensive security at the Olympic venues, Matthew Olsen, director of the National Counterterrorism Center, said, “The greater threat is to softer targets in the greater Sochi area, and in the outskirts.”

On Iran, Clapper warned that a move by Congress to impose new sanctions could unravel a deal reached last year to ease economic penalties on Tehran in return for shutting down key parts of its nuclear program. North Korea, meanwhile, has expanded its uranium enrichment facility, he said, and restarted a plutonium reactor, following through on recent threats to resume nuclear weapons work.