BAGHDAD, IRAQ: An increasingly common site in Baghdad: Iraqi police with machine guns are deployed to escort a Ministry of Interior official through Baghdad. (Aaron C. Davis/THE WASHINGTON POST)

The assassins strike quietly, often just after dark, as Iraq’s political and military leaders speed home surrounded by armed guards.

The dead in April alone included generals, police commanders, a deputy minister and the head of Iraq’s tax agency. The wounded included a member of parliament, a judge and the head of the national theater, survivors of attacks on their motorcades.

Among 50 targeted killings last month, most were carried out by gunmen using silenced weapons, according to Iraq’s Interior Ministry, which oversees the country’s police forces.

Assassinations are not an entirely new feature of Iraq’s political landscape. But a stealthy string of killings that began last month has given them new prominence, shaking Iraqis’ confidence in their government’s ability to protect them and raising questions about the country’s security just months before the last U.S. troops are scheduled to withdraw.

In recent days, Prime Minister Nouri al-Maliki and members of parliament have felt compelled to address the killings repeatedly in public, vowing all-out efforts to stop them.

BAGHDAD, IRAQ: Members of an Iraqi police explosives unit look for evidence after a bomb was detoated near a military checkpoint , wounding two officers and a child in Baghdad's Jadriya neighborhood. (Aaron C. Davis/THE WASHINGTON POST)

But the killings have continued with at least 14 more dead from gun attacks and targeted bombings, mostly against police officials, in the first three days of May. Late Tuesday, a car bomb killed at least 15 people and wounded more than 30 in a Shiite neighborhood in Baghdad.

Iraqi intelligence officials and U.S. military officers say the killings are being waged from both ends of Iraq’s religious and political spectrum, as part of renewed jockeying for power in advance of the American pullout.

According to Iraqi officials, Sunni extremists, including the insurgent group al-Qaeda in Iraq and former members of Saddam Hussein’s Baath Party, who still consider Iraq’s elected government illegitimate, are behind most of the recent slayings. But they say Shiite Muslim militias, some with close ties to Iran, also appear to be conducting some of the killings to assert influence and settle scores.

Ali al-Dabbagh, Iraq’s chief government spokesman, said there was no evidence that Shiite militias are behind the assassinations. But he acknowledged that the sheer number of killings of high-placed government officials has become a serious problem. “This is a new way of terrorism here in Iraq,” Dabbagh said. “This is a big threat for the whole process, the whole government.”

Assassinations accounted for roughly 20 percent of about 251 violent deaths in Iraq last month. The death toll is orders of magnitude smaller than what Iraq endured during the height of the country’s sectarian bloodshed in 2006 and 2007, when more than 2,000 Iraqis died in violent attacks each month. Iraq’s overall homicide rate is now lower than in most American cities.

Calling the tactic “sick,” Ad Melkert, the United Nations special representative in Iraq, said he alerted the Security Council last year to the increasing frequency of assassinations.  Maj. Gen. Jeffrey S. Buchanan, the senior U.S. military spokesman in Iraq, said the country’s security forces recorded an average of 20 assassinations in recent months and just more than 30 in March. Buchanan said that was more than the United States would classify strictly as assassinations but called the trend “worthy of concern” even before April’s spike more than doubled the recent average.

The intensity of the recent assassinations has attracted lurid coverage in the Arabic-language media, with haunting details of the previous night’s attacks recounted each morning in television and newspaper reports across the country.

Iraqi intelligence officials say the killers include gunmen who have stalked Iraqi bureaucrats with semiautomatic weapons muzzled with silencers. Others have been masked men on motorbikes who slap magnetic “sticky bombs” on motorcades carrying political and military elite.

In response, some police officers said they have refused to drive their state-run pickup trucks, shunning any vehicles with Iraqi government markings as “caskets.” Iraq’s intelligence agencies have acquired scores of beat-up taxis for agents and high-ranking officials so they can disguise themselves on their way to and from work.

To cut off potential escape routes, security forces have erected new roadblocks and checkpoints in recent days, contributing to traffic gridlock.

“It’s a new, blind kind of insurgency,” said Ahmen Riyad, 25, a police officer who was directing traffic this week at an intersection adorned with makeshift memorials to three assassinated police officers, including two killed recently by gunmen using silencers.

In recent congressional testimony, State Department officials have described Iraq as “relatively stable” as the roughly 50,000 U.S. troops still in the country begin to prepare for departure.

A front group for al-Qaeda in Iraq recently asserted responsibility for most of the killings in recent months. In a posting on an extremist Web site, the Islamic State of Iraq listed the names of 62 government employees and security workers it said it had killed, including 22 assassinated with silenced weapons.

In an interview deep inside one of Iraq’s police compounds, Maj. Gen. Hussein Kamal, the domestic intelligence chief, said the government has information suggesting that remnants of the country’s Baathist regime might have returned to Iraq in recent months from Syria.

But he said Sunni insurgents are not the only force behind the recent killings. Kamal said Shiite extremist groups, most notably Asaib Ahl al-Haq, which has ties to Iran, seem to be behind some of the killings, targeting anyone perceived as against them, he said.

Marisa Cochrane Sullivan, an expert on Shiite extremist groups in Iraq and the deputy director of the Institute for the Study of War in Washington, said she thinks the increase in assassinations has less to do with Iraq’s neighbors attempting to compound turmoil in the Middle East than jockeying for superiority for when U.S. forces leave. “It’s a very uncertain time, and groups are trying to work now to influence in their favor.”

Special correspondent Aziz Alwan contributed to this report.