BAGHDAD (AP) – A parked car bomb ripped through a packed outdoor market in southwestern Baghdad on Tuesday morning, killing 25 people and injuring 60 others, despite a 3-month-old security crackdown meant to reduce violence in the capital.

The deadly blast occurred about 10 a.m. in the Shiite-dominated neighborhood of Amil, damaging a nearby medical center, turning buildings into charred husks and setting a line of cars on fire, police said.

The neighborhood has seen an increase in violence in recent weeks, and Sunni politicians expressed fears that Shiite militiamen had resumed their campaign of sectarian cleansing in Amil and nearby neighborhoods of southwestern Baghdad.

“There were four women around my stall when we heard a loud explosion, which threw me many meters away from my stall,” said Fadhil Hussein, 32, who sells spices in the market and suffered shrapnel wounds in his back and head. “I found myself in a pickup truck with other people. Some of them were bleeding and yelling.”

Sami Hussein, 25, was heading to the market with her 5-year old son when she heard the blast, “followed by gray and black smoke, which engulfed the market and made me to fall on the ground.”

She suffered shrapnel wounds in her face and legs.

“I lost my son, and have no idea about his fate,” she said. Medical officials at the hospital said her son had been killed in the explosion.

The blast came amid the American and Iraqi security operation meant to flush out insurgents and restore order to Baghdad. However deadly attacks targeting civilians and police have continued.

American military officials say that insurgent groups, feeling the pressure from the crackdown, have hit back by stepping up their car bombing attacks with their devastating death tolls. A May 6 bombing in a market in the Baiyaa district, killed 30 people and injured 80 others.

A few minutes before the bombing in Amil, which adjoins the neighborhood where the May 6 blast occurred, gunmen in two cars drove through the nearby Khadra neighborhood and ambushed a civilian car carrying three plainclothes police officers from the major crimes unit, killing two and wounding the third, police said.

Police and other Iraqi security officers have been heavily targeted by insurgents, who accuse them of collaborating with American-led forces in the country.

Another police officer was killed when a roadside bomb exploded next to a police patrol driving through an eastern Baghdad neighborhood about 9 a.m., police said. Three other officers were injured in the attack.

Later Tuesday, two mortar shells slammed into a teacher’s college affiliated with Baghdad University, killing three students and injuring seven others, police said.

The violence came as American politicians debated how long American troops will remain in Iraq. A senior American official warned Monday that the Bush administration may reconsider its support if Iraqi leaders do not make major reforms by fall.

The American official, who briefed reporters on condition his name not be published, did not say what actions could be taken by the White House, but his comments reflected the Bush administration’s need to show results in Iraq – as an answer to pressure by the Democrats in Congress seeking to set timetables on the American military presence.

Also Monday, British troops clashed with Shiite Muslim gunmen in the southern city of Basra. Britain’s military said one British soldier and a civilian driver were killed when a supply convoy was attacked in the center of the city, Iraq’s second biggest.

Elsewhere, American troops raided safe houses south of Baghdad but failed to find three soldiers missing since a May 12 ambush that left four other Americans and an Iraqi dead.

“We’ve (identified) some safe houses and we targeted a couple of those today and they were able to slip away from us. But we’re going to come at things from a different angle,” an American spokesman, Major Webster Wright, said without elaborating.

American officers said the search by thousands of America. and Iraqi soldiers may be forcing the kidnappers to move the three Americans frequently, preventing insurgents from posting pictures of their captives on the Internet.

“We choose to be cautiously optimistic,” Major General Rick Lynch told CNN. “We’re pursuing all leads with a passion, but right now we believe our soldiers are still alive. Each day that passes when we don’t see proof of life, it causes us concern.”

With violence raging, pressure is mounting on Prime Minister Nouri al-Maliki’s government to demonstrate progress on key reforms or risk losing American support for the unpopular war.

Defense Minister Abdul-Qader al-Obeidi said that Iraq’s military was drawing up plans to cope with any quick American military pullout.

“The army plans on the basis of a worst case scenario so as not to allow any security vacuum,” Mr. al-Obeidi said. “There are meetings with political leaders on how we can deal with a sudden pullout.”

It was unclear whether al-Obeidi’s comment referred to routine contingency planning or reflected a feeling among Iraqi leaders that the days of American support may be numbered even though President Bush blocked an effort by Congress to set a withdrawal timetable.

A White House spokesman, Tony Fratto, said Bush expressed confidence in al-Maliki during a telephone call Monday to the Iraqi leader.

He said the two talked about political progress in Iraq, and al-Maliki gave Bush updates on two key American demands – legislation to share Iraq’s oil wealth among its regions and ethnic groups and a reform of the constitution. The officials spoke on condition of anonymity because they were not supposed to release the information.

Prospects for far-reaching agreements among Sunnis, Shiites and Kurds were thrown into doubt over the weekend when the leader of the largest Shiite party, Abdul-Aziz al-Hakim, was diagnosed with lung cancer at a hospital in Houston. U.S. officials had been counting on al-Hakim to help push through reforms.