Washington, June 25 (RHC)-- Documents provided by the former U.S. National Security Agency (NSA) contractor have shown that British intelligence service aided Washington's controversial targeted killing outside recognized war zones, two reports say.

Documents leaked by Edward Snowden show tight cooperation between the NSA and Britain's Government Communications Headquarters (GCHQ) relation to drone strikes outside recognized war zones, The Guardian and The New York Times have reported.

The reports indicate that GCHQ may have given American intelligence agencies essential intelligence before a 2012 US drone strike in Yemen. The files shed light on a joint US, UK and Australian program codenamed Overhead, which was aimed at developing individual tracking abilities -- essential to drone strikes in both Yemen and Pakistan.

Jemima Stratford QC, a leading barrister, was requested by The Guardian to review classified documents provided by Snowden. “Assuming that the documents which I have seen are genuine, in my view they raise questions about the extent to which UK officials may have had knowledge of, or helped to facilitate, certain US drone strikes which were not carried out in the context of an international armed conflict,” Stratford said.

“These documents underline why greater transparency as to UK official policies would help to ensure legality from a domestic and international law perspective,” she added.

British officials have so far refused to comment on the reports or give any information about involvement with the US assassination drone programs. Washington uses unmanned aerial vehicles in an alleged bid to target terrorists in Yemen, Pakistan, Afghanistan, Somalia, and elsewhere. However, local officials and witnesses say the drone strikes mostly kill civilians. The legality of the drone strikes has also been questioned multiple times by international lawyers and human rights groups.

Ed Snowden left the U.S. in June 2013 after leaking classified intelligence documents, stored on encrypted files, revealing the extent of the NSA’s spying activities, and was granted asylum by Russia in August 2013.