New Zealand has been involved in spying operations in Bangladesh, sharing intelligence with the United States as part of its global counter-terrorism campaign, secret documents show.

United States fugitive Edward Snowden worked at the US National Security Agency (NSA) before turning whistleblower in June 2013, releasing documents to the mainstream media showing spy agencies were conducting mass surveillance.

New documents obtained by Snowden and released to nzherald.co.nz reveal the Government Communications Security Bureau (GCSB) has been involved in surveillance of Bangladesh for more than a decade.

A "top secret" NSA information paper from April 2013 says the GCSB "has been the lead for the intelligence community on the Bangladesh counter-terrorism (CT) target since 2004."

The global counter-terrorism campaign was launched by the US in the wake of the September 11 attacks in 2001.

The Bangladesh operation was described by the NSA as one of New Zealand's "success stories".

The paper says the GCSB had provided "unique intelligence leads that have enabled successful CT operations by Bangladesh State Intelligence Service, CIA [US Central Intelligence Agency] and India over the past year".

Bangladesh's three main security agencies are the Directorate General of Forces Intelligence, the National Security Intelligence and the Rapid Action Battalion (RAB). The three agencies have been accused of severe human rights abuses, including extra-judicial killing and torture.

Another report, from 2009, describes how the spying is planned by a GCSB unit named "OCR", the Signals Intelligence Development Team.

That report says there is a special collection site in Dhaka, the Bangladesh capital, which is used by the GCSB to intercept local mobile phone calls.

While the documents show how the GCSB was sharing intelligence with Bangladesh's security agencies, at the same time it was also monitoring the internal communications of Bangladesh's RAB.

The 2009 report says the "RAB has been an active target for the GCSB in the past and this information could well be of high interest for future operations if the domestic security situation in Bangladesh were to deteriorate".

The Green Party said on Thursday that the GCSB was dragging New Zealand into human rights abuses in Bangladesh.

Bangladeshi security agencies - which the GCSB had passed information to - were known to target, torture and kill a range innocent people including ethnic and religious minorities, political opponents, reporters and labour movement activists, Greens co-leader Dr Russel Norman said.

Human rights abuses by government security agencies in Bangladesh were "so widespread and systematic" the GCSB could not say for certain the information it had given to those agencies was not used for human rights abuses.

"[Prime Minister] John Key has always justified the GCSB on the basis that it is there to protect the good guys, but these documents reveal that it is helping the bad guys," he said..

"Most New Zealanders would find this deplorable and agree that this is not within the mandate of the GCSB."