The action follows the murders in September of an eight-member Ebola education team attacked by angry locals in Womey, a town at the epicentre of the deadly outbreak.
The army has been deployed in the town since the killings, and many inhabitants have fled to the surrounding forests, fearing reprisals by troops, according to residents and journalists who recently visited.
"We are on hunger strike to demand the demilitarisation of Womey and the return of all local residents to their homes," said the group's spokesman Faya Millimono, the leader of an opposition party.
He and around 20 lawmakers, politicians, civil society activists and private citizens have not eaten since Monday, he said as they gathered at the country's parliament in the capital Conakry.
Millimono said around 6,000 villagers were camped out in the forests surrounding Womey, although the claim could not immediately be independently verified.
"We want to attract the attention of the national and international community to the drama playing out amid total indifference in Womey," Holomou Kourouma, another opposition lawmaker in the group.
Guinean human rights minister Khalifa Gassama Diaby called for the withdrawal of the army from Womey.
He described the murders as "odious" but said in a statement that they did not justify "the logic of collective punishment, excessive and unjustified limitations on freedoms".
The victims, including three journalists, went missing after their delegation came under attack during an outreach visit to Womey.
Eight bodies were recovered from the septic tank of a nearby primary school two days later.
The deadliest Ebola epidemic on record has killed around 5,000 people in west Africa and infected more than twice that number, according to the World Health Organization.
The virus emerged in Guinea at the start of the year and has infected 1,760 Guineans, killing more than 1,000.
The spread in Guinea has been accompanied by fear and paranoia by villagers who feel the government and the international community cannot be trusted.
Many Guineans believe local and foreign healthcare workers are part of a conspiracy to either deliberately introduce the outbreak, or invented it as a means of luring Africans to clinics to harvest their blood and organs.
At least 21 people were wounded during violent scenes in which the team was pelted with stones, according to local police.