The country’s biggest party comes only a week after eight top officials, including the ex-police and intelligence chief, were sentenced to death for allegedly attempting a coup in 2009.
Meanwhile the former police chief and former head of the anti-drugs agency are on trial for alleged involvement in drug-trafficking.
The flashy “Freedom Day” celebrations are seen as a kick in the teeth for many Gambians who observers say live in fear of the iron-fisted Jammeh.
“Having become paranoid, President Yahya Jammeh sees coups everywhere,” said Dakar-based human rights group Raddho in a statement on Tuesday.
“Since coming to power more than 200 coups d’état have been identified in a country where… a reign of intimidation and terror spare neither political actors nor civil society.”
Jammeh seized power via a bloodless coup in 1994, and was later elected president three times. He is running for a fourth term in 2011.
Addressing a rally in western Gambia on Sunday after a nationwide tour Jammeh said: “Whether you like it or not, no coup will end my government, no elections can end my government. By God’s grace I will rule this country as long as I wish and choose someone to replace me.”
The 45-year-old leader brushes aside regular condemnations from human rights bodies and the international community, and has in the recent past booted two UN officials out of the country.
In September 2009 he threatened to kill those who attempted to “destabilise” the country by working with “so-called defenders of human rights”.
Raddho said the death sentences handed down last week were “the tip of the iceberg” for a regime accused of cracking down on the press, unlawful arrests, summary executions, witch hunts and other abuses.
Despite the criticism Jammeh is credited with bringing development, roads and schools to Gambia.
On Monday he inaugurated a five-star hotel worth $41m in Banjul and a $5.5m bridge connecting the central part of the country to the south.
On Wednesday Jammeh will lay the foundation stone for a $10m parliament building.
Jammeh has constructed a brand new venue in Banjul for the July 22 celebration, which an official from the Dakar-based Coalition for Human Rights in the Gambia called “the day democracy was buried” in the country.
Speaking on condition of anonymity, the official said recent arrests and lawsuits as well as constant reshuffling of cabinet posts and regularly replacement of army chiefs were “a clear indication of (Jammeh’s) despotic nature, he doesn’t want any form of challenges”.
“You have to understand that the president is a highly intolerant person. People who are around him, he sees them as a threat and unfortunately his reaction is always very harsh and very brutal.”
The tiny West-African country with a population of 1.5 million people which nestles inside Senegal, is a popular tourist destination with its sandy beaches and swaying palms which attract thousands of visitors every year.
While growth in the Gambia reached 5.9% in 2008, according to the World Bank, poverty is widespread, with 67% of the population living on less than $1.25 a day.
“It is good to have big buildings and big hotels, but it is even better for people to have their basic freedoms,” said the official from the Coalition for Human Rights.
Amnesty International will be holding a protest march in Dakar on Thursday against Jammeh’s “repressive regime” and similar demonstrations will take place around the world.
Raddho called on “the international community and Africa to put pressure on Jammeh that he pardon those sentenced to death and stop the gross violations of human rights that have become commonplace in this country.”