Fourteen US soldiers were killed in a helicopter crash overnight in northern Iraq, the US military has said.
The Black Hawk helicopter, carrying 10 soldiers and four crew members, crashed after experiencing a mechanical malfunction, a US statement said.
There were reportedly no indications of hostile fire, but the cause of the crash is still under investigation.
Later, at least 20 people died when a suicide bomber drove a fuel tanker into a police station in Baiji, police said.
The head of the local hospital in the oil city, 180km (110 miles) north of Baghdad, said both police and civilians were among the victims. At least 50 people were wounded.
The police had only just moved into the building after a similar attack in June destroyed the old station and killed at least 10 people.
MAJOR US LOSSES IN IRAQ
2 Nov 03: Chinook helicopter downed near Falluja, killing 16
15 Nov 03: Two Black Hawk helicopters collide avoiding ground fire in Mosul, killing 17
21 Dec 04: Suicide bomb at military base in Mosul kills 19
26 Jan 05: CH-53E helicopter crashes in West Iraq, killing 31
3 Aug 05: Roadside blast near Haditha kills 14 marines
1 Dec 05: Ten marines killed by roadside bomb near Falluja
20 Jan 07: Black Hawk crashes near Tal Afar, killing 12
24 Apr 07: Suicide bombing of base near Baquba kills nine
22 Aug 07: Black Hawk helicopter crashes in northern Iraq, killing 14 soldiers
The 14 US soldiers killed on Wednesday were part of Task Force Lightning, a division responsible for a large area of northern Iraq, including the cities of Balad, Kirkuk, Tikrit, Mosul and Samarra.
A second Black Hawk helicopter had been flying alongside at the time.
It is not clear precisely where the helicopter came down.
It was the deadliest such incident since January, when another Black Hawk went down in Diyala province.
The worst US helicopter crash in Iraq was in January 2005. Thirty marines and a sailor were killed when a Super Stallion came down in bad weather near the Jordanian border.
The BBC's Mike Wooldridge in Baghdad says the fairly frequent loss of helicopters over the past four years has demonstrated the dependence of US forces on them - and their vulnerability.