Gambian forces routinely commit abuses, with a paramilitary group allowed to act with impunity, a new report by Human Rights Watch claims.
Political opponents and critics of ruler Yahya Jammeh are regular targets, says the report, the first into The Gambia by HRW investigators.
One man was reportedly forced to drink cooking oil, while others had melted plastic bags dripped on to their skin.
The Gambian government has declined to comment on the report to the BBC.
The report was based on interviews with 35 victims and witnesses of violations committed mainly over the last two years in the west African nation.
Much of it focuses on the actions of Gambia’s National Intelligence Agency, a group also known as the Jungulers, who are loyal to President Jammeh.
Their reported torture methods include rape, near-suffocation with plastic bags and electric shocks.
President Jammeh has ruled The Gambia with a firm hand since he came to power in a coup 20 years ago.
He has also implemented tough measures against the country’s lesbian, gay, bisexual and transgender (LGBT) community. He has called gay people “vermin” and threatened to slit their throats.
Homosexual acts are illegal in The Gambia and MPs passed a bill last August imposing life sentences for “aggravated homosexuality”.
HRW said one gay man was beaten with clubs and threatened with death if he did not name other gay men.
While the European Union withdrew nearly $15m (£9.7m) in funding from The Gambia last year, HRW is not calling on other donors to follow suit.
“So long as security forces and paramilitary groups act with impunity, Gambians will suffer,” said Felicity Thompson, the group’s West Africa researcher.