An American soldier was killed in a roadside bombing north of Baghdad, the U.S. military said Friday, making April the deadliest month for American forces in Iraq this year.

Also Friday, American troops, acting on tips from Iraqi intelligence, killed the reputed al Qaeda boss of Samarra, where a Shiite shrine bombing two months ago nearly plunged the country into civil war.

CountryWatch: Iraq

The latest American death, which occurred Thursday evening, brought the number of U.S. troops who have died this month in Iraq to at least 67.

Although that figure is well below some of the bloodiest months of the Iraq conflict, it marks a sharp increase over March, when 31 American service members were killed. January's death toll stood at 62 and February's at 55. In December 2005, 68 Americans died.

Reasons behind the rising U.S. deaths were unclear, and U.S. military officials have cautioned not to interpret cyclical changes as the beginning of a trend. Some U.S. officers have suggested the increase could be due to better weather this month, making it easier for insurgents to launch attacks.

The increase in U.S. deaths comes at a time when the U.S. military says sectarian violence among Iraqis is declining after a sharp rise in the wake of the Feb. 22 bombing in Samarra. That triggered reprisal attacks against Sunni mosques and clerics.

In a briefing Thursday, Maj. Gen. Rick Lynch told reporters sectarian attacks in the Baghdad area had fallen by 60 percent last week, diminishing fears of civil war.

That could also indicate militants were shifting their attacks on U.S. and Iraqi forces, their traditional targets throughout the three-year insurgency.

Al Qaeda in Iraq leader Abu Musab al-Zarqawi warned in an Internet video this week that U.S. "dreams" in Iraq "will be defeated" and "what is coming is even worse."

In a possible sign of a shift, insurgents launched simultaneous attacks Thursday on police stations and checkpoints around Baqouba, 35 miles northeast of Baghdad.

At least 58 people were killed and 74 arrested in two days of clashes, Maj. Gen. Ahmed al-Awad said. They included 49 insurgents, seven Iraqi soldiers and two civilians, Iraqi and U.S. officials said.

The raid on the purported al Qaeda in Iraq safehouse took place about nine miles north of Samarra, U.S. officials said. The target of the raid, Hamadi Tahki al-Nissani, was killed when he tried to escape, a U.S. statement said.

Two other insurgents were killed, one of them as he tried to throw a grenade, the statement added.

Al-Nissani was believed to be the leader of al Qaeda in Iraq cells in Samarra, 60 miles north of Baghdad, U.S. officials said. The city was an al Qaeda in Iraq stronghold until U.S. troops regained control two years ago.

Meanwhile, the spokesman of a Sunni Arab political party said in an interview on Iraqi state television that two members of an undisclosed militia group have been detained in the slaying of Vice President Tariq al-Hashimi's sister.

Mayson al-Hashimi, 60, was slain Thursday by gunmen firing from a car as she left her home in a southwestern neighborhood. Her bodyguard was also slain. Two weeks ago, the vice president's brother, Mahmoud al-Hashimi, was shot and killed while driving in a mostly Shiite area of Baghdad.

Party spokesman Dhafer al-Ani gave no further details except that one of the detained militia members was wounded. He did not specify whether the suspects were from a Sunni or Shiite group but said they were not members of al Qaeda in Iraq.

Interior Ministry officials said they were unaware of any arrest. Al-Ani told The Associated Press he learned of the arrests from the Iraqi army.

Meanwhile, former leader Saddam Hussein, who is being tried in Iraq on charges of crimes against humanity, turned 69 on Friday. Small pro-Saddam rallies were staged in his hometown of Tikrit and a Sunni district of Baghdad.

In Najaf, a Shiite holy city where opposition to the former regime runs deep, dozens of people mocked the ousted ruler in a rally during which a man wearing a Saddam mask rode on a horse through the streets alongside a police escort.

In other violence Friday:

— Two mortars or rockets were fired at the heavily fortified Green Zone. One landed inside the zone but failed to detonate, while the other exploded on the other side of the Tigris River, the U.S. military said.

— A roadside bomb killed an Iraqi policeman and wounded two in southwestern Baghdad, police said.

— Police found the corpses of two middle-aged Iraqi men in a mostly Sunni Arab neighborhood of western Baghdad. Two other bodies were found in Kut, police said.

— An Iraqi soldier was killed in Ramadi, where American soldiers exchanged gunfire with insurgents, U.S. officials said. No U.S. casualties were reported.