WASHINGTON, 30 November 2003 — More US troops have died in Iraq in November than in any month since the war began last March, according to Defense Department figures.

With November nearly over, the official death count Friday stood at 79, surpassing March (65) and April (73), when the invasion was underway and fighting was most intense and widespread.

The surge reflects an increase in the effectiveness and the frequency of guerrilla attacks.

About half of the deaths resulted from the downing of four military helicopters, in which 39 soldiers were killed. US aircraft in Iraq have been targeted in the past, but these incidents, involving either a surface-to-air missile or rocket-propelled grenade, marked the first major hits.

Most of the other US combat fatalities occurred in ground attacks by enemy fighters using weapons that have become characteristic of their resistance: Guns, rocket-propelled grenades and remote-controlled explosives.

At one point during the month, military officials reported that the number of guerrilla attacks was averaging more than 40 a day. In response to the heightened activity, US troops intensified their tactics, engaging in a stronger show of force that included greater use of artillery, tanks, attack helicopters, F-16 fighters and AC-130 gunships to pound targets throughout central Iraq. The rate of assaults on US forces then dropped to fewer than 30 a day.

In contrast to the higher combat deaths in November, the number of accidental deaths — 11 — stayed comparatively low.

In all, 437 troops have died in Iraq since the war began, 2,094 have been listed as wounded in action and 2,464 have suffered noncombat-related injuries, ranging from accidental gunshots to broken bones and injuries in vehicle accidents. Since May 1, when President Bush declared the end of major combat operations in Iraq, 298 troops have died.

As the numbers have mounted, administration officials have offered various responses in an attempt to cushion the impact on public opinion and avoid a collapse in support for the Iraq operation.

Officials have noted that most attacks on US forces have occurred in central Iraq, with the rest of the country less menacing. They’ve emphasized the improvements being made to Iraq’s public facilities, the revival of economic activity and the steps toward self-rule.

They’ve also cited a rapid growth in the number of Iraqi security forces, now exceeding 145,000, who are to relieve some of the burden on the 130,000 US troops in country and allow for a reduction to about 110,000 by spring.

Earlier this week, a senior general with the Coalition Provisional Authority suggested the rising US casualty rate should not be taken as a sign that the United States is losing the war, especially when compared with enemy casualties.

“The casualties that we put on the enemy far exceed the casualties they inflict on us,’’ Army Brig. Gen. Mark Kimmitt said at a news conference in Baghdad.

He offered no figures for enemy dead or wounded, however. As a rule, the Pentagon does not publicize such numbers, to avoid the frequent enemy body counts that marked the Vietnam War and ultimately proved a poor measure of US military performance.

Defense Secretary Donald Rumsfeld this week provided one partial figure for enemy dead, indicating the Pentagon is keeping some tally on the damage US forces are doing to the ranks of Iraqi guerrillas. In the week ended Nov. 23, he said, US forces had killed 40 to 50 enemy fighters and wounded 25 to 30.