Nearly 100 Democratic lawmakers on Monday urged President Donald Trump's administration to press Colombia over attacks on rights activists and warned that US assistance should not contribute to surveillance.

A UN report earlier this year found that 108 human rights defenders were killed last year in Colombia, with activists of indigenous and African descent hit especially hard.

"Colombia is now the most dangerous country in the world for human rights defenders," the 94 members of the Democratic-controlled House of Representatives wrote in a letter to Secretary of State Mike Pompeo.

They called for pressure on conservative President Ivan Duque, a close US ally, to "stop this tragedy."

"We urge you, Mr. Secretary, to ensure that all agencies of the United States speak with one clear voice to condemn these ever escalating murders," said the letter spearheaded by Representatives Jim McGovern and Mark Pocan, leaders of the Congressional Progressive Caucus.

Women take part in a protest against violence in Medellin, Colombia, in June 2020
Women take part in a protest against violence in Medellin, Colombia, in June 2020 AFP / JOAQUIN SARMIENTO

The lawmakers called for the United States "to press the Duque administration to take the necessary steps to identify and prosecute the intellectual authors of these crimes and dismantle the criminal structures that protect them."

They also warned they were watching the nature of US aid, which amounts to $528 million in the current fiscal year, after accounts that Colombian intelligence has spied on activists and journalists.

US financial help must not "assist, aid or abet such illegal surveillance, now or in the future," they wrote.

Colombia in 2016 signed a landmark peace agreement with FARC rebels that end a half-century of conflict.

But security remains dangerously lax in impoverished areas formerly controlled by the rebels as they lay down their arms.

The lawmakers said that illegal arms groups were filling a vacuum amid the COVID-19 pandemic, "further increasing the vulnerability of targeted rights defenders and local leaders."