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An international human rights group has accused Yemen of failing to investigate the 2011 killing of 45 anti-government protesters during the uprising against former President Ali Abdullah Saleh.

Human Rights Watch says in a report released Tuesday that top former officials — including Saleh's relatives, such as his nephew — should be held responsible for the slayings.

The New York-based group was referring to the March 18, 2011 incident, when the government unleashed security forces on the demonstrators in the capital, Sanaa.

Saleh stepped down last year, following year-long protests against his rule.

HRW's senior researcher Letta Tayler warned that "if Yemen doesn't fairly investigate and prosecute those responsible for this deadly attack, it risks perpetuating the culture of impunity at the heart of Yemen's uprising."