"These deaths could have been prevented. Most deaths were accompanied by weeks and months of threats."

By Anna Pujol-Mazzini

LONDON, May 16 (Thomson Reuters Foundation) - Murder, surveillance and trolling - some of the tools used against rights campaigners across the globe as attacks surge to "unprecedented" levels, Amnesty International said on Tuesday.

The rights group has launched a campaign to shed light on the dangers that campaigners - who can be lawyers, journalists, students or victims of abuse - face as they work to protect human rights.

"What we are witnessing today is a full-frontal assault by governments, armed groups, corporations and others with power on the very right to defend human rights," Salil Shetty, Amnesty's secretary general, said in a statement.

Amnesty's "Brave" campaign will also highlight individuals under attack for their work, such as jailed Cambodian land rights campaigner Tep Vanny and Finnish transgender rights defender Sakris Kupila, who he says was threatened for his campaigning against sterilisation as a requirement for gender change.

In an almost two-fold increase from 2015, 281 campaigners were killed in 2016, according to rights group Front Line Defenders.

On average, a human rights defender has been killed every other day since a 1998 U.N. declaration seeking to protect them, according to Amnesty.

"These deaths could have been prevented," Guadalupe Marengo, who heads the human rights defenders programme at Amnesty, told the Thomson Reuters Foundation.

"Most deaths were accompanied by weeks and months of threats," she added.

Campaigners for women's rights and lesbian, gay, transgender and bisexual (LGBT) rights were at particular risk as they faced the threat of sexual violence and smear campaigns on top of attacks due to their work, Amnesty said in a report.

"It is much harder because they face the same discrimination as others but also other discrimination that includes sexual innuendos, threats of rape, smear campaigns," Marengo said.

Recent advances in technology allowed for increased mass surveillance online and misinformation campaigns used to discredit the work of campaigners and journalists, making their work more dangerous, the report added.

(Reporting by Anna Pujol-Mazzini @annapmzn, Editing by Ros Russell. Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters that covers humanitarian news, women's rights, trafficking, property rights, climate change and resilience. Visit http://news.trust.org)

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