Nato says one of its helicopters that crashed in the southern Afghan province of Helmand on Wednesday may have been shot down by the Taleban.
Seven people died in the crash, five of them US crew. Two military passengers - one British, one Canadian - also died.
Nato-led troops are fighting militants nearby. Dozens of Taleban were killed or injured, Afghan officials say.
Elsewhere, at least 16 policemen died in a Taleban ambush in southern Zabul province, the interior ministry said.
Fighting between Nato-led security forces and the Taleban has escalated in recent weeks - particularly in the south.
Nato is still investigating the cause of Wednesday's crash, but says it looks as if Taleban claims to have shot the Chinook down may well be correct.
RECENT AFGHAN AIR CRASHES
18 February 2007 - Eight US troops die in helicopter crash in Zabul province
2 September 2006 - 14 UK service personnel die in Nimrod crash in Kandahar province
31 August 2006 - Dutch F-16 fighter pilot dies in crash in south of country
27 July 2006 - 16 people of multiple nationalities die in helicopter crash in south-east
6 May 2006 - 10 US soldiers die in helicopter crash in Kunar province
24 April 2006 - Five die when US anti-drugs plane crashes in southern Afghanistan
"It was a hostile area where the helicopter went down," said Major John Thomas, a spokesman for Nato's International Security Assistance Force (Isaf).
"Initial indications are that enemy fire may have brought down the helicopter."
The helicopter crashed at around 2100 (1630 GMT) in the Kajaki district of Helmand, Isaf said in a statement.
A rescue patrol was ambushed by "enemy fighters" and forced to call for an air strike to access the crash site, Isaf said.
Incidents of helicopters being shot down are relatively rare in the country, says the BBC's Alastair Leithead in Kabul.
About 30,000 alliance troops and another 10,000 US-led ones have been battling to boost the authority of President Hamid Karzai.
On Thursday, Isaf confirmed that fighting was going on against the Taleban in Sangin district, near Kajaki.
A statement said air strikes had been carried out against Taleban positions. It did not say whether there had been any casualties.
But the Afghan Defence Ministry said dozens of Taleban fighters had been killed or wounded.
Local people have disputed the government account, saying some of those killed were civilians rather than Taleban.
Sangin district police chief Ghulam Wali told the BBC the aim of the operation was to secure the road from the Shali area to Kajaki.
In the ambush in Zabul, six policemen were injured as well as those killed, officials said.
Interior Ministry spokesman Zmaray Bashary told the BBC that police had also inflicted heavy casualties on their attackers in a gun battle which had raged for 20 minutes.
He said the ambush took place in Shahjoy district, a Taleban stronghold, as the police convoy travelled from Zabul to Ghazni.
There was no way of independently verifying casualty figures in either incident.