They are deadly, hard to detect and fast becoming one of the most sought-after weapons in the air defence industry.

Global demand for unmanned aerial vehicles (UAVs), better known as drones, is heating up as armed forces invest in new systems to boost their ability to carry out reconnaissance and strikes without putting soldiers' lives in danger.

Propelled by a rise in Asian defence budgets, annual global spending on UAVs is forecast to almost double from the current $5.9 billion to $11.3 billion over the next decade, according to US-based defence research firm Teal Group.

The Asia Pacific is the second largest buyer after the United States.

"Almost every country in the region is trying to get their hands on drones or develop their own ... Thailand, India, Singapore, Japan, Australia, Korea," said Jon Grevatt of IHS Jane's Defence Weekly.

Home to more than half the world's population, Asia also has some of the biggest potential flashpoints from North Korea, to the South China Sea, South Asia and Afghanistan.

"UAVs are necessary in this age when you want to win wars and at the same time you want to have less casualties," said Tommy Silberring, who heads the drone division at Israel Aerospace Industries (IAI).

IAI, which pioneered the development of UAV technology for the Israeli military in the 1970s, was one of several defence manufacturers showing off drones at last week's Singapore Airshow.

The use of drones rather than manned aircraft helps make countries participation in multilateral war efforts more palatable to the public, said Silberring, a former Israeli air force colonel.

"You really don't want to tell your people that you are giving the lives of your soldiers for another country," he told AFP at the air show.

Drones have played a crucial role in recent conflicts, with the United States relying on them to strike targets in the rugged tribal areas of Pakistan that are strongholds of Taliban and Al-Qaeda operatives.

US drones were also used in the NATO-led intervention in Libya last year.

According to IAI, its Heron UAVs are used by 18 customers around the world, including Singapore's air force, which displayed its Heron 1 at the show.

The Heron TP -- the largest in the Israeli drone arsenal with the wingspan of a Boeing 737 passenger jet -- is purported to have a range of more than 7,400 kilometres (4,600 miles).

In the United States, homegrown manufacturers such as General Atomics and Northrop Grumman look set to benefit from the Pentagons recent plans to expand its current fleet of 7,494 drones by 30 percent.

According to a congressional report released in January, the US military is expected to spend nearly $32 billion on new UAVs over the next eight years.

"Over the next few years, we will definitely see an aggressive growth of unmanned systems being used by US forces around the world," said Commander Robert Moss, a regional director at the United States Office of Naval Research Global.

"There is a wide range of uses for unmanned systems, from surveillance work, gathering atmospheric data to direct combat strikes," he told AFP.

This burgeoning demand has spurred Asian manufacturers to enter the market, which has long been dominated by Israeli and US companies.

"We want to be in the unmanned arena but we are selective because there are already so many big players in the industry," said Patrick Choy, vice president of international marketing at ST Engineering, a Singapore-based defence manufacturer.

ST Engineering launched the Skyblade 360, the latest addition in a series of mini UAVs, at the airshow.

Its predecessor, the Skyblade III, is used by the Singapore Armed Forces to provide reconnaissance and surveillance for ground forces.

Choy emphasised that ST Engineering had no intention of competing with Israeli and US manufacturers to build large UAVs.

"We want to build a niche in the tactical area, where we are able to help small units with our UAV technology," he told AFP.

"Unless you are a global power, you cannot convince customers to buy big UAVs which require supporting technology like satellites".

India is similarly modest about its Rustom-1 drone, a model of which was on display at the trade fair.

"Our main priority is to enhance the current capability of the Rustom... we have no intentions of exporting it," said Parimal Kumar, a senior official from India's Defence Research and Development Organisation.

IAI's Silberring is unfazed by the nascent Asian drone manufacturers, and said demand for Israeli drones would remain high.

"You just cannot compete with us... we look 20 years ahead to make sure we have products in the market no one will have," he said.