DR Congo President Felix Tshisekedi on Monday paid tribute at a genocide memorial on the sidelines of an economic forum in Rwanda, a highly symbolic gesture in bilateral relations badly hobbled by the 1994 bloodbath.
The Twitter account of the genocide memorial published a video of Tshisekedi, who was elected in January, laying a wreath at the memorial in Kigali, a diplomatic first.
The gesture came ahead of the 25th anniversary on April 1 of the start of the massacre, in which at least 800,000 people -- mainly minority Tutsis and moderate Hutus -- were killed in 100 days.
After the carnage, many of the men who carried out the massacres fled into eastern Democratic Republic of Congo, destabilising the region to this day.
Tsishekedi's tribute sparked anger in the DRC.
Some on social media blasted Rwandan President Paul Kagame for his record on human rights and for Rwanda's own reputed role in the turmoil in the east of the country.
Many Congolese accuse of Rwanda of arming and supporting rebel militias, pillaging the DRC's mineral wealth.
A rights group, the Struggle for Change (Lucha) also drew attention to the DRC's own bloody past, which includes Belgium's brutal colonial occupation and two civil wars in the past quarter of a century.
"When will there be memorials and an official commemoration for the millions of dead Congolese, from (Belgian King) Leopold II to the wars and violence of these last 25 years?" it asked.