Suspected Saddam Hussein loyalists are held at the prison
A mortar attack has killed two US soldiers at a giant prison complex west of Baghdad and a third serviceman has been killed by a roadside bomb.
A military spokeswoman said the attack on the US-run Abu Ghreib prison on Saturday evening had left two soldiers dead and 13 wounded.
No inmates were hurt.
A separate bomb blast killed a US soldier in a vehicle near Ramadi, about 100 kilometres (60 miles) west of Baghdad on Saturday night, the US military said.
The growing insurgency has heightened international concern about the US strategy in Iraq.
In a major initiative to help rebuild the shattered economy, the Iraqi interim administration has announced that foreign investors will be allowed to buy complete control of previously state-owned enterprises - apart from those in the oil sector.
Foreign banks will be able to buy Iraqi financial institutions, while the central bank itself will become independent.
UN debate on Iraq
At the same time, a delegation from the US-appointed Iraq Governing Council has set off for New York to attend a UN General Assembly meeting that opens on Tuesday.
But the delegates left without Aqila al-Hashimi, a council member seriously wounded in the stomach, shoulder and leg by gunmen who opened fire on her car in western Baghdad on Saturday.
Aqila al-Hashimi came under a hail of gunfire in Baghdad
The only former Baath party member to serve on the council, she is reported to be in a stable condition and out of danger after a second operation for gunshot wounds.
She had been rushed to Yarmouk hospital in Baghdad before being transferred to a US military facility.
Ms Hashimi is thought to be the first member of the 25-member Governing Council to have suffered an assassination attempt.
A Shia Muslim, she is one of three women on the council, set up by US administrator Paul Bremer in July as part of efforts to hand power over to Iraqis.
Iraqi insurgents have launched daily attacks on US-led forces. The Americans have now lost 79 troops as a result of hostile fire since 1 May, when President George W Bush declared major combat operations to be over.
The BBC's Caroline Hawley in Baghdad says the US forces are trying to train more Iraqis to police the country. They are also strengthening the defences of sprawling palace complexes built for Saddam Hussein and now used as bases.
But the Americans say they are facing attacks not only from former regime "remnants" but also from foreign Islamic militants.
President Bush is seeking support at the UN for a new resolution that would authorise a multinational force for Iraq.
The Iraq Governing Council delegation hopes to occupy Iraq's seat at the UN, but the Security Council remains deeply divided over the US occupation, with major powers including France and Germany demanding a more significant UN role.
Abu Ghreib, Iraq's most notorious prison under Saddam Hussein, has been attacked frequently since it was taken over by the Americans shortly after the war.
Six Iraqi detainees were killed and 59 others wounded in a mortar attack on Abu Ghreib on 16 August, and last week a US military spokeswoman said the prison was coming under fire "four nights out of seven".
It is a vast, heavily fortified complex 20 kilometres (12 miles) outside the Iraqi capital, with at least five separate enclosures.
Tens of thousands of political prisoners were held there by Saddam Hussein's regime - and many were tortured and executed.
Now, it is being used to hold hundreds of suspected Saddam Hussein loyalists, as well as common criminals. Many are living in tents surrounded by razor wire.