Thousands of Egyptian protesters remained in Cairo's Tahrir Square Thursday to press their demand for immediate resignation of the country's military leaders.

Protest organizers have called for another mass demonstration on Friday.

Earlier Thursday, military rulers rejected the call to immediately transfer power to civilian rule.

Major General Mukhtar el-Mallah, of the Supreme Council of the Armed Forces, said the move would amount to a “betrayal” of trust.

In a Thursday news conference, military leaders said parliamentary elections would begin as scheduled on Monday. They also apologized for the deaths of at least 35 people in a series of clashes between security forces and demonstrators this week.

The apology was issued as a fragile truce took hold in Tahrir Square, which had been a flashpoint for the violent skirmishes between police and protesters.

The unrest had continued in spite of concessions that were announced earlier this week by Field Marshal Hussein Tantawi. The head of the Supreme Council of the Armed Forces pledged to speed the transition to civilian rule with presidential elections before July 2012.

In another development, Egyptian authorities are releasing three American students who were arrested during a protest in Cairo this week.

Egyptian media reports said the Americans, who were students at the American University in Cairo, were detained along with other protesters while throwing petrol bombs at police.