The United States has made a lot of progress in the 100 days since the end of major combat in Iraq, President George W Bush has said.
At least two Iraqis were shot dead in a Tikrit market
He grieved the loss of US soldiers, but urged Americans to be patient.
Earlier on Friday, US snipers killed at least two Iraqis whom they said were selling weapons in Saddam Hussein's home town of Tikrit in northern Iraq.
The killings came a day after the US military signalled it planned to act less aggressively amid fears of alienating the Iraqi public.
President Bush, speaking to reporters at his ranch in Texas, appeared upbeat despite daily attacks on US troops and Thursday's deadly car bomb attack on Jordan's embassy in Baghdad.
"We've got a lot of brave soldiers slowly but surely demolishing elements of the Baathist regime, those foreign terrorists who feel like they can use Iraq to arm up and inflict casualties or perhaps gain strength to come and attack Americans elsewhere," Mr Bush said.
In Tikrit, north of Baghdad, US forces had placed snipers around a market, after hearing that weapons and ammunition were sold there every Friday, a US commander said.
"We didn't give them a chance to engage us. If you walk around with weapons in a city, you become a combatant," said Lieutenant Colonel Steve Russell.
But a spokesman at the main hospital in Tikrit told AFP news agency US troops had killed three people and injured five others, including two children.
US officials said a third man was captured at a hospital where he was being treated for wounds and a fourth, also believed to be wounded, was on the run.
In a separate incident, a US soldier died of gunshot wounds while on guard duty in western Baghdad on Thursday.
US military authorities have not said whether the soldier died from a hostile attack.
There are 150,000 US troops in Iraq
Fifty-five Americans have died in such attacks since President George W Bush declared hostilities in Iraq largely over on 1 May.
Mr Bush would not say whether he agreed with the commander of the US forces in Iraq, Lieutenant General Ricardo Sanchez, who on Thursday said troops would stay in Iraq for at least two years.
"I will do what's necessary to win the war on terror," he said.
General Sanchez has signalled a change in military tactics by saying his troops' "iron-fisted" approach was provoking retaliation.
But the BBC's Jonathan Head in Baghdad says the scenes in Tikrit illustrate all too starkly how difficult it will be for the US forces to soften their approach.
The US military spokesman in Baghdad, Colonel Guy Shields, has suggested that any change in tactics would be limited.
"The rules of engagement have not changed," he said.
"We're still going to conduct raids, but what General Sanchez was referring to is that now with all the increased intelligence that we're getting, we can be more precise and go to a specific location which means that you don't have to disrupt such a large area."
US Secretary of State Colin Powell has said the US-led military coalition may want to "stand back a little" and rely more on local forces to maintain security.