Bento quits as Sporting coach
"Paulo Bento presented his resignation as head coach as he understands he no longer has the conditions to be in charge of the team," the club said in a statement.
The statement said Bento's assistant Leonel Pontes would coach the team until further notice.
Bento, 40, who played for Sporting and local rivals Benfica, became Sporting coach in 2005 and led the side to four consecutive runners-up places in the league.
He was under growing pressure as a poor run of results, exacerbated by the team's unconvincing performances, had left Sporting in seventh place in the league after last season's second position.
Bento was booed throughout Thursday's match against Ventspils with fans waving white handkerchiefs to signal they wanted a change of manager.
After Sporting's 1-1 home draw with Maritimo on Sunday, police fired shots into the air to disperse a crowd of fans who showed their discontent by trying to break into the club headquarters.