CAIRO — When Egypt’s liberal activists began planning a demonstration to criticize President Mohammed Morsi’s failure to fulfill the lofty promises he set for his first 100 days in office, they had good reason to expect they would have Tahrir Square to themselves on a day they dubbed “Accountability Friday.”

Their vision of mobilizing once more in the square — this time in unity against Islamist control of post-revolution Egypt — did not materialize. The day ended with more than 100 injured after hours of clashes between the activists and Muslim Brotherhood members. It was the first incident of violence between the rival camps since long-time Brotherhood member Morsi took office in late June.

The dust is still settling after Friday’s clashes in Tahrir, but the basic sequence of events shows the current balance of power in the country. The struggle for Tahrir was another indication that the voices of Islamists are drowning out those of liberal activists seeking to be heard in Egypt’s still-rocky transition.

In the run-up to Morsi’s 100th day in power, opposition parties and liberal groups called for a “million-man march” on Tahrir aimed at rallying non-Islamist forces.