Extremist militant groups and terrorists across the world and in the Middle East are benefiting greatly from the security leaks made by former US National Security Agency (NSA) contractor Edward Snowden , the head of Britain's domestic intelligence service said Tuesday.
MI5  Director General Andrew Parker, in an unusually frank and open statement, warned that the security of the UK and the US has been jeopardised by Snowden's leaks and that they weakened that ability of the security services to stop those plotting deadly attacks against the West, Reuters reported.
Though he did not namecheck Snowden , Parker issued a warning on the danger of disclosures about the work of Britain's listening agency, known as GCHQ, whose capabilities were made public by media reports based on documents from Snowden stole, according to Reuters.
The far-reaching extent of US and British surveillance was exposed by media reports based on previously top secret documents stolen by Snowden, prompting a spy scandal that pitted Barack Obama  against the Kremlin and triggered calls for greater scrutiny of Western agents, Reuters said.
Cautioning against complacency over the threat from militants, especially those returning from the battlefields of Syria , the M15 chief dismissed claims that British spies "gratuitously rummaged" through the private data of foreign countries, according to Reuters.
"It causes enormous damage to make public the reach and limits of GCHQ techniques. Such information hands the advantage to the terrorists. It is the gift they need to evade us and strike at will," Reuters reported Parker as saying in his first public speech taking up his post as MI5 chief on April 22.
Previous leaks made by Snowden revealed that terrorist and extremist groups, many of them based in the Middle East, have made numerous attempts to infiltrate America's intelligence agency the CIA .
Although the file did not go into detail over the nature of the applicants' extremist or "hostile" ties, it said that Hamas, Hezbollah and Al Qaeda and its affiliates were the groups trying to access the intelligence agencies most often .
According to the document, which was published by The Washington Post in early September, the NSA's fear of infiltration was so strong they planned last year to investigate at least 4,000 staff who obtained security clearances, AFP reported.