Two US soldiers have been killed and two others injured in Iraq after their vehicle was hit by a roadside bomb in the capital, Baghdad.
The attack was similar to a blast that killed five soldiers on Friday
The bomb went off at dawn on Saturday in the eastern slum district of Sadr City, near the site of an attack in which five soldiers died on Friday.
Witnesses said the injured men were taken away by military helicopters.
The attack was just one of a spate of attacks, despite a truce taking hold in the holy city of Najaf.
Spate of killings
Unconfirmed reports suggested a convoy of two sports utility vehicles - the favoured vehicle for foreign civilian contractors - had been ambushed on the road to Baghdad airport.
Two or three people had been killed, news agencies quoted both American and Iraqi sources as saying - one describing how the bodies had been burnt and mutilated after the attack.
However, there has been no official confirmation of the deaths.
Meanwhile, in the northern city of Mosul, the brother of the man who is suspected to have led US forces to Saddam's sons was shot dead by gunmen.
Salah al-Zidani was brother of Nawaf al-Zidani - who is thought to have collected $30m for revealing the location of Uday and Qusay, both killed last July by American forces.
Nawaf has not been seen since then and is thought to have fled Iraq.
After the Baghdad bomb attack, a local resident said he had heard the blast: "I saw a small car just like an armoured vehicle damaged."
Hassan Sami told the APTN news agency, "An American helicopter landed and evacuated them. Some of the victims were evacuated in armoured vehicles."
There was no immediate indication of who was behind the bombing.
There has been a string of similar attacks in recent weeks, prompting fears of an increase in violence in the run-up to the 30 June transfer of sovereignty.
On Friday, five US soldiers were killed and five others wounded in an attack on a convoy near Baghdad's main Shia Muslim district.
More than 490 US soldiers have been killed in attacks since President George W Bush declared major combat operations over in May 2003.