approximately 180 a day last month, reflecting an increasingly complicated conflict that includes sectarian clashes of Sunni and Shiite militias on top of continuing strikes by insurgents, criminal gangs and al-Qaeda terrorists, according to the directors of the CIA and the Defense Intelligence Agency.

"No single narrative is sufficient to explain all the violence we see in Iraq today," Gen. Michael V. Hayden, the CIA director, told the Senate Armed Services Committee on Wednesday.

Attempting to describe the enemy, Lt. Gen. Michael D. Maples, the DIA director, listed "Iraqi nationalists, ex-Baathists, former military, angry Sunni, Jihadists, foreign fighters and al-Qaeda," who create an "overlapping, complex and multi-polar Sunni insurgent and terrorist environment." He added that "Shia militias and Shia militants, some Kurdish pesh merga, and extensive criminal activity further contribute to violence, instability and insecurity."

In unusually harsh terms, the two intelligence directors spelled out how quickly the violence in Iraq has escalated this year, from about 70 attacks a day in January to about 100 a day in May and then to last month's figure. "Violence in Iraq continues to increase in scope, complexity, and lethality" despite operations by the Iraqi government and the U.S.-led coalition, Maples said. He described "an atmosphere of fear and hardening sectarianism which is empowering militias and vigilante groups, hastening middle-class exodus, and shaking confidence in government and security forces."

"The longer this goes on, the less controlled the violence is, the more the violence devolves down to the neighborhood level," Hayden added. "The center disappears, and normal people acting not irrationally end up acting like extremists."

Although the Bush administration continues to emphasize the role of al-Qaeda in Iraq, Maples described the current situation as "mostly an intra-Arab struggle to determine how power and authority will be distributed," with or without the U.S. presence. Al-Qaeda and foreign terrorist numbers were put at roughly 1,300, while Hayden, pressed by senators, estimated the number of insurgents in the "low tens of thousands." Maples estimated the number of Iraqi insurgents, including militias, at 20,000 to 30,000, and said there are many more who supply support.

Asked about the brazen kidnapping in Baghdad on Tuesday of some 100 employees in the Sunni-led Ministry of Education by an apparent Shiite group in commando uniforms using Interior Ministry vehicles, Hayden said the CIA station chief in Iraq said it showed that the battlefield "is descending into smaller and smaller groups fighting over smaller and smaller issues over smaller and smaller pieces of territory."

Hayden said he believes that the turning point in the fighting came in February with the bombing of the Askariya mosque in Samarra. The destruction of the revered Shiite site by Sunni-based al-Qaeda terrorists unleashed what Hayden described as "historic forces" that have created "the satanic level of violence" of today.

"Sectarian violence now presents the greatest immediate threat to Iraq's stability and future," he said.

Underlying the sectarian fighting are not only deep-rooted religious differences, but also the more recent political history of Shiite suffering under the iron rule of Saddam Hussein and his Sunni- and Baathist Party-dominated government.

The Shiites, who make up more than half of Iraq's population, now want to make certain they control the new Iraqi government and to assure themselves that the Hussein group never regains power. "This fear of a return to Baathism is almost palpable among Shia elites," Hayden said.

As a result, the Shiites have maintained control of the Interior Ministry and the police. "Militias often operate under protection or approval of Iraqi police [when they] attack suspected Sunni insurgents and Sunni civilians," Hayden said. In addition, "radical Shia militias and splinter groups stoke the violence."

At the same time, Hayden said, there are fissures within the Shiite groups, and their "power struggles . . . make it difficult for Shia leaders to take actions that might ease Sunni fears." Adding to the problem is Iran, which is supporting even competing Shiite factions. "Iranian involvement with the Shia militias of all stripes . . . has been quite a new development," Hayden said.