Watchdog urges Morocco to release jailed W Sahara journalist
Haddi's "physical condition is extremely worrying, after 78 days on hunger strike", RSF said in a statement.
"He is now in danger of dying and must be released without delay," RSF secretary general Christophe Deloire said.
"We issue an urgent appeal to the Moroccan authorities to end his ordeal."
Haddi was arrested in 2010 after "covering the use of force by the Moroccan authorities to dismantle the Gdeim Izik protest camp" in Western Sahara, RSF said.
Three years later he was sentenced to 25 years in prison for "violence with intent to kill officials carrying out their duties" at the camp during clashes with protesters.
Western Sahara is a former Spanish colony, mostly under Morocco's control, where tensions with the pro-independence Polisario Front have simmered since the 1970s.
Morocco has offered autonomy but maintains the territory is a sovereign part of the kingdom.
Haddi was working for a Polisario-run Sahrawi television channel at the time of his arrest, RSF said, adding that he began a hunger strike on January 13 to denounce poor treatment in prison.
Moroccan authorities consider Haddi a pro-independence activist and say he was jailed for taking part in the alleged "murder" of 11 security forces during clashes at Gdeim Izik.
After the violence, a Moroccan military court sentenced 23 Sahrawi activists to jail terms ranging from 20 years to life.
Moroccan authorities have denied Haddi's family visitation rights, RSF said.
But Moroccan prison authorities have rejected the claim. A Moroccan state-run human rights group said on March 3 that Haddi's health was "normal" and denied he was observing a hunger strike.
Haddi's "mistreatment... has continued for too long," Deloire said.
"It is time to end the torture and rescue this journalist from the hunger strike he has been following for more than two months and from the oblivion to which he has been consigned by a (protracted) conflict."