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The MQ-4C Triton unmanned aircraft system completes its inaugural cross-country ferry flight at Naval Air Station Patuxent River, Maryland in this US Navy photo Reuters

Drone strikes and "targeted killings" of terror targets by the United States can be counterproductive and bolster the support of extremist groups, the CIA has admitted in a secret report released by WikiLeaks.

The document, by the intelligence agency's Directorate of Intelligence, said that despite the effectiveness of "high value targeting" (HVT), air strikes and special forces operations had a negative impact by boosting the popular support of terror organisations.

The CIA report is dated 2009 and talks of operations conducted in countries such as Iraq, Pakistan, Somalia, Afghanistan and Yemen.

Operations against terror targets "may increase support for the insurgents, particularly if these strikes enhance insurgent leaders' lore, if non-combatants are killed in the attacks, if legitimate or semi-legitimate politicians aligned with the insurgents are targeted, or if the government is already seen as overly repressive or violent," the report said.

The US has used drone strikes on terror targets in the Middle East and south Asia, in areas considered too dangerous to send a large number of ground troops to eliminate those considered a threat to US national security.

The report spoke of how Israel's "targeted-killings campaign" was limited in its effectiveness because of "decentralised command structures, compartmented leadership, strong succession planning, and deep ties to their communities, making the[se] groups highly resilient to leadership losses".

"Israeli HVT efforts from 2000 to 2002 strengthened solidarity between terrorist groups and bolstered popular support for hard-line militant leaders, according to US Embassy officials in Jerusalem and clandestine reporting," the study says.

It also documents the problems faced when launching a targeting campaign against various groups, such as the Taliban and al-Qaeda in Iraq (AQI).

"Senior Taliban leaders' use of sanctuary in Pakistan has also complicated the HVT effort," it reveals.

"Moreover, the Taliban has a high overall ability to replace lost leaders, a centralised but flexible command and control overlaid with egalitarian Pashtun structures, and good succession planning and bench strength, especially at the middle levels."

It speaks of drone strikes also having limited effect in Iraq on AQI, who "initially lost several iterations of its senior leadership and numerous local emirs, but these losses initially did little to slow AQI's momentum".

According to the Bureau of Investigative Journalism, US drone strikes have killed between 2,400 and 3,888 people in Pakistan in the years 2004 to 2014 and between 371 and 541 people in Yemen in the years 2002 to 2014.