New Zealand’s eavesdropping agency used an Internet mass surveillance system to target government officials and an anti-corruption campaigner on a neighboring Pacific island, according to a top-secret document.

Analysts from Government Communications Security Bureau, or GCSB, programmed the Internet spy system XKEYSCORE to intercept documents authored by the closest aides and confidants of the prime minister on the tiny Solomon Islands. The agency also entered keywords into the system so that it would intercept documents containing references to the Solomons’ leading anti-corruption activist, who is known for publishing government leaks on his website.

XKEYSCORE is run by the National Security Agency, and is used to analyze billions of emails, Internet browsing sessions and online chats that are collected from some 150 different locations worldwide. GCSB has gained access to XKEYSCORE because New Zealand is a member of the Five Eyes surveillance alliance alongside the United States, the United Kingdom, Canada and Australia.

A number of GCSB’s XKEYSCORE targets are disclosed in a top-secret document that was obtained by The Intercept and New Zealand newspaper the Herald on Sunday. The document raises questions about the scope of the surveillance and offers an unprecedented insight into specific people monitored by New Zealand’s most secretive agency.

The targets list, dated from January 2013, was authored by a GCSB analyst. It is contained in a so-called “fingerprint,” a combination of keywords used to extract particular information from the vast quantities of intercepted data swept up by XKEYSCORE. None of the individuals named on the list appear to have any association with terrorism.

Most of the targets, in fact, had a prominent role in the Solomon Islands government. Their roles around the time of January 2013 suggest GCSB was interested in collecting information sent among the prime minister’s inner circle. The targets included: Barnabas Anga, the permanent secretary of the Ministry of Foreign Affairs and External Trade; Robert Iroga, chief of staff to the prime minister; Dr Philip Tagini, special secretary to the prime minister; Fiona Indu, senior foreign affairs official; James Remobatu, cabinet secretary; and Rose Qurusu, a Solomon Islands public servant.

The seventh person caught up in the GCSB’s surveillance sweep is the leading anti-corruption campaigner in the Solomon Islands, Benjamin Afuga. For several years he has run a popular Facebook group that exposes corruption, often publishing leaked information and documents from government whistleblowers. His organization, Forum Solomon Islands International, has an office next door to Transparency International in Honiara, the capital city of the Solomon Islands. GCSB analysts programmed XKEYSCORE so that it would intercept documents sent over the Internet containing the words “Forum Solomon Islands,” “FSII,” and “Benjamin Afuga.”

Each of the named targets was contacted by the Herald on Sunday prior to publication. Several were not reachable or did not respond to a request for comment. Robert Iroga, who was the prime minister’s chief of staff at the time his name appeared on the list, criticized the surveillance and said it would paint a “pretty bad image” for New Zealand.

“I’m shocked to hear about the intrusion of the New Zealand government into the sovereign affairs of a country like ours,” Iroga said. “Any intervention in this way to get information from the Solomon Islands is highly condemned.”

Benjamin Afuga, the anti-corruption campaigner, said he was concerned the surveillance may have exposed some of the sources of the leaks he publishes online.

“I’m an open person — just like an open book,” Afuga said. “I don’t have anything else other than what I’m doing as a whistleblower and someone who exposes corruption. I don’t really understand what they are looking for. I have nothing to hide.”

A spokesman for Manasseh Sogavare, the recently elected prime minister of the Solomon Islands, said the issue would be addressed through “diplomatic channels.”

The Solomon Islands are about 2,300 miles north of New Zealand and have a population of some 550,000 people, according to United Nations figures. In the late 1990s and early 2000s the islands suffered from ethnic violence known as “The Tensions.” This led to the 2003 deployment to the Solomons of New Zealand, Australian and Pacific Island police and military peacekeepers. By January 2013, the date of the target list, both New Zealand and Australia were focused on withdrawing their forces from the island country and by the end of that year they were gone.

The XKEYSCORE list shows New Zealand was carrying out surveillance of several terms associated with militant groups on the island, such as “former tension militants,” and “malaita eagle force.” But with the security situation stabilized by 2013, it is unclear why New Zealand spies appear to have continued an expansive surveillance operation across the government, even tailoring XKEYSCORE to intercept information about an anti-corruption campaigner.

Andrew Little, leader of New Zealand’s Labour Party, told the Herald on Sunday the surveillance was at odds with the country’s diplomatic relationship with the Solomons. “You would assume we have relations with government at the highest level and constructive dialogue,” he said.

The surveillance may have been part of a secret attempt to intercept information about The Truth and Reconciliation Commission, an inquiry that was set up by the Solomon Islands in the aftermath of the ethnic violence. The commission was modeled on South Africa’s post-apartheid process and launched by Bishop Desmond Tutu during a 2009 visit to the Solomons. The XKEYSCORE list includes the keywords “Truth and Reconciliation Commission,” “TRC,” and “trc report.” Moreover, Afuga, the targeted anti-corruption campaigner, worked with the commission as a project coordinator.

GCSB declined to comment for this story. In a statement, the agency’s acting director, Una Jagose, said: “The GCSB exists to protect New Zealand and New Zealanders. We have a foreign intelligence mandate. We don’t comment on speculation about matters that may or may not be operational. Everything we do is explicitly authorized and subject to independent oversight.”

A spokesman for New Zealand prime minister John Key also declined to comment. The spokesman said: “New Zealand’s intelligence agencies have been, and continue to be, a significant contributor to our national security and the security of New Zealanders at home and abroad.”

In recent weeks, The Intercept has published a series of stories about the extent of New Zealand’s surveillance in collaboration with the New Zealand Herald, the Herald on Sunday, and The Sunday Star-Times. Earlier disclosures, which were based on documents from NSA whistleblower Edward Snowden, have exposed the country’s broad surveillance across the Asia-Pacific. The revelations have shown how a surveillance base in the Waihopai Valley is funneling bulk data into the XKEYSCORE system and they have also exposed that New Zealand is targeting some its strongest trading partners for surveillance and then sharing the data with the NSA.

Photo of Honiara, the capital city of the Solomon Islands. (Lonely Planet Images/Getty.)