By Alastair Leithead
BBC News, Kabul
High-ranking British officers in Afghanistan say they need more air power to assist ground troops, who are facing increasing violence.
British troops in Helmand are facing increasing violence
The calls come after a week of intense clashes with Taleban fighters in the southern province of Helmand.
Sources have told the BBC that more transport and attack helicopters and medical evacuation planes are needed.
The British military has about 4,000 troops in Afghanistan. They are part of a Nato-led taskforce.
The International Security Assistance Force (Isaf) is a United Nations-mandated organisation.
There have been mutterings from the capital Kabul for some time about the lack of aircraft, but it has recently become a serious concern as levels of violence increase.
Helmand is one of Afghanistan's toughest areas
The Chinook transport helicopters are running to their limits and often beyond, operating in very high temperatures for long hours. There has also been a call for more Apache attack helicopters.
This week in Helmand around 50 soldiers were ambushed on three sides by Taleban militia.
The troops had to fight intensively at close quarters for two hours because the air support was already in use in another part of the province.
British troops in action
Training Afghan security forces
Counter-narcotics in Helmand
Rebuilding roads and schools
More worrying is the lack of aircraft for medical evacuations, when demand has been high.
Three soldiers have been killed in Helmand - a Taleban stronghold - in two weeks and others injured.
On Tuesday, two British soldiers were killed in fighting with Taleban forces.
The troops were part of a "planned detention operation" in Sangin, when they were attacked by Taleban militia in a gun battle which lasted an hour.
The third killed, Captain Jim Philippson, 29, from 7 Parachute Regiment Royal Horse Artillery, died on Sunday 11 June when a mobile patrol became involved in a firefight against suspected Taleban forces.
The bulk of the British military's 4,000 troops in Afghanistan are in Helmand.
They are there to help train Afghan security forces, facilitate reconstruction, and provide security, the defence secretary has said.
In Helmand, the emphasis is also on counter-narcotics, as the province is the "largest single source of opium in Afghanistan".
The British military began increasing its deployment from about 1,100 troops in early 2006, and the number is expected to peak briefly at 5,700 before dropping to about 4,500 as engineering staff withdraw in the middle of the year.