Police spokesman George Bardue says police are pursuing suspects but have made no arrests after the incident early Saturday.
Voters in the West African nation went to the polls Tuesday.
Opposition parties say they’re pulling out of the recent presidential polls which they called “flawed” and say they won’t accept the results.
A Saturday statement from eight opposition parties including those of the second- and third-place candidates say the electoral commission manipulated vote-counting in favor of President Ellen Johnson Sirleaf.
The statement also called for a Sunday rally but gave no details.
Sirleaf led late Friday with 45.4 percent of the vote, falling short of the majority needed to avoid a runoff, according to partial results.
The Harvard-educated Sirleaf faced 15 challengers on Tuesday. She is viewed abroad as a reformer and was awarded this year’s Nobel Peace Prize for her role in stabilizing Liberia after a 14-year civil war.
