BAGHDAD, Iraq — With the help of Iraqi civilians, U.S. forces yesterday captured six men suspected of downing a civilian helicopter and shooting to death the lone survivor.

Across the country, Iraqi insurgents struck with bomb attacks, killing at least 16 people, including a U.S. soldier.

The suspects in the helicopter downing were caught after an Iraqi civilian told U.S. soldiers from Task Force Baghdad that he knew where insurgents had stashed a blue KIA pickup that had been used in the attack and led them to the site, the military said.

Soldiers searched two nearby houses shortly after midnight yesterday, arresting three men and seizing bomb-making material in the first home. Three suspects were grabbed from the second residence and all were being questioned, the military said.

Col. Clifford Kent, a spokesman for the 3rd Infantry Division, which oversees the 1st Armored Division's troops in Iraq, said residents near Taji provided U.S. troops with "detailed descriptions of the individuals, as well as their vehicles and where they live."

Although no evidence was found directly linking the detained men to the helicopter attack, Kent said local witnesses reported "the suspects being in the near vicinity of the attack at the same time it happened."

U.S. forces did not identify the captives or say where they were taken into custody.

The Russian-made Mi-8 helicopter, flying from Baghdad to Tikrit, was shot down about 12 miles north of the capital on Thursday. The dead included six American bodyguards for U.S. diplomats, three Bulgarian crew members and two security guards from Fiji.

Two groups claimed responsibility for the attack and released video to support their claims.

In one video, insurgents are seen capturing and shooting to death the lone survivor, identified as a Bulgarian pilot.

The aircraft was owned by Heli Air of Bulgaria and chartered by Toronto-based SkyLink Aviation. The six Americans were employed by Blackwater Security Consulting, a subsidiary of security contractor Blackwater USA of Moyock, N.C. Four of the company's employees were slain and mutilated by insurgents in Fallujah a year ago.

In other violence, a car bomb exploded outside a police academy in northern Iraq today, and when police set up a checkpoint to close off the area, a second car bomb exploded nearby, authorities said. At least six Iraqis were killed and 25 wounded, a hospital official said.

The coordinated attack in Tikrit, the hometown of Saddam Hussein, occurred just as new police recruits were about to leave the academy and travel to Amman, Jordan, for a training program, said police Lt. Shalan Allawi. Tikrit is 80 miles north of Baghdad.

At Tikrit General Hospital, Dr. Mohammed Ayash said four policemen and two civilians were killed by the bombs, and 23 policemen and two civilians wounded.

South of the capital, three insurgents were killed today as the roadside bomb they were trying to plant in the town of Mahawil exploded, police said in the nearby city of Hillah.

Yesterday, Associated Press Television News cameraman Saleh Ibrahim was shot and killed when gunfire broke out after an explosion in the northern city of Mosul, 225 miles northwest of Baghdad.

Iraq has experienced a surge in militant attacks that have caused heavy casualties in recent weeks, ending a relative lull after the country's historic Jan. 30 elections. Iraqi leaders are struggling to form a Cabinet that will include members of the Sunni minority, believed to be the driving force in the insurgency.

A series of explosions shook the Iraqi capital yesterday. The most deadly was a roadside bomb that exploded near an Iraqi army convoy on the outskirts of the city, killing nine soldiers and wounding 20, police said.

Some of the surviving soldiers opened fire in response, shooting and killing the driver of a civilian car, police said.

Elsewhere in Baghdad, a car bomb targeting a U.S. patrol detonated on a busy road that links to the perilous highway leading to the airport. One Iraqi was killed and seven wounded, hospital officials said. Three U.S. soldiers also were injured in the blast, which knocked down power lines and destroyed one military and two civilian vehicles, U.S. forces said.

In al-Haswah, west of Baghdad, a U.S. soldier assigned to the 155th Brigade Combat Team, II Marine Expeditionary Force, was killed when a roadside bomb exploded near the convoy in which he was traveling, the U.S. military said.

At least 1,566 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an Associated Press count.

Also yesterday, police said:

• An Iraqi civilian was killed by a roadside bomb on a highway in Samarra, 60 miles north of Baghdad.

• A roadside bomb hit an Iraqi army convoy in Mosul, wounding three soldiers.

• Mortars slammed into an Iraqi military base in southern Baghdad, injuring seven soldiers.

Information from the Los Angeles Times on the helicopter-attack arrests was included in this report.