"Three cars in the Polish convoy were destroyed in the attack," he said.
Officials described the attack as an assassination attempt.
Bartosz Weglarczyk, the deputy foreign editor of Gazeta Wyborcza, told Al Jazeera that the attack was "well planned".
"Iraq is still under foreign occupation and Iraqis continue to die in great numbers"
Send us your views
"It was just two or three blocks away from the Polish embassy in Baghdad," he said.
"It means the attack [had been] planned for a long time. The attackers knew who was in the convoy and what their target was."
Reuters Television pictures showed a European-looking man with his head, leg and hands bandaged being evacuated in a helicopter which had landed in the street.
Iraqi soldiers said the man, who was surrounded by security guards and troops, was the Polish ambassador.
They said other wounded people had been taken to the so-called Green Zone for treatment.
Pietrzyk was being treated for burns, Waldemar Figaj, the deputy ambassador, said later.
"He is going to be fine," he said.
Jaroslaw Kaczynski, the Polish prime minister, said that Poland would not withdraw its troops from Iraq in response to the attack.
"Desertion is always the worst option," Kaczynski said.
"This is a difficult situation, but those who became engaged and were there for years and then withdrew are making the worst possible mistake."
Poland backed the US-led invasion of Iraq in 2003 which toppled Saddam Hussein, the Iraqi president at the time.
At the height of its involvement, Poland had 2,500 soldiers in Iraq, though it currently has about 900 troops in the country and the mission has lost popular support at home.
Poland's ruling party, which faces a snap election on October 21, supports extending the Iraq mission beyond the end of the year even though a majority of Poles want the the soldiers to return home.
Some opposition parties are also calling for an end to the mission.
Weglarczyk told Al Jazeera: "What happened in Baghdad today will change nothing.
"Poles don't like to be pushed to do something and we don't like to be threatened ... I don't think it will change the attitude of Polish society toward the Iraq war."
A number of diplomats have been killed in Baghdad since the invasion began.
Last year four Russian diplomats were abducted and killed and in 2005 fighters said they had killed Ihab el-Sherif, the Egyptian mission chief.
In the same year, Bahrain's envoy was also shot and wounded when fighters opened fire on his car.