The country appeared on the verge of serious unrest, even a coup d'etat, as Congress planned to discuss whether to oust the President, Abdala Bucaram.
The demonstrators were calling on the country's legislators to dismiss the President who said he would refuse to go.
As many as 4,000 protesters, angered by the gunfire, threw rocks and petrol bombs at the security forces guarding the doors to the Congress building. After police responded with teargas, the protest quickly dissipated, according to a local radio station.
A Congress spokesman identified one of those injured in the violence as a spokesman for a political party, the Popular Democratic Movement. The other, according to Radio Quito, was a photographer for a local newspaper.
Mr Bucaram, who relishes the nickname "el loco" (the madman), threatened to "assume all the powers available to protect the legitimacy of the popular will".
That appeared to hint at the sort of Latin American autogolpe, or do- it-yourself coup, used by the Peruvian President Alberto Fujimori to dissolve Congress and cling to power in 1995.
Mr Fujimori at the time had the support of the military. Whether Mr Bucaram, elected last year, has similar support appeared doubtful. Troops surrounded the Congress building last night, ostensibly to protect the single chamber's 82 legislators from a growing crowd of protesters who had flocked to the area.
The crisis, brought on by a series of price rises last month, followed a 48-hour general strike and widespread protests against Mr Bucaram's unorthodox style and alleged corruption. Militant trade unions said they would continue the strike indefinitely until Mr Bucaram stands down or is impeached.
In a nationwide address last night before Congress met, Mr Bucaram sacked his brother and other members of a clique - of Arab origin like himself - and said he would rescind some of the price rises.
His opponents in Congress suggested he might be voted out by a simple majority - 42 votes - as "mentally incapacitated" under Ecuadorean law. His supporters insisted a two-thirds majority would be necessary and that the opposition could not find that many votes.
Cesar Gaviria, President of the Organisation of American States, flew urgently to Quito saying Ecuador's democracy was in danger. The US State Department urged Ecuadoreans to refrain from further violence.