TUNIS—Tunisia's interim government is struggling to establish control over an agitated nation amid sustained public protests and strikes, adding to uncertainty about what so far has been a peaceful transition since the surprise ouster of President Zine al-Abedine Ben Ali.

In a stark rebuke to the government's legitimacy, an estimated 90% of Tunisia's schoolteachers obeyed orders by their powerful union to strike on Monday, according to the state news agency, defying a government order to reopen schools as part of an attempt to normalize daily life following the turmoil that ended Mr. Ben Ali's 23-year rule.

The teachers are expected to be joined in the strike by university lecturers on Tuesday, when colleges and universities had been due to reopen. Mr. Ben Ali ordered the closure of all state schools two weeks ago.

Groups of protesters from small towns in the south and central parts of the country slept in front of the prime minister's residence Monday for the second night in a row, ignoring emergency laws in place for the last two weeks that instituted a nighttime curfew through the capital. The demonstrators are demanding the resignations of Prime Minister Mohammed Ghannouchi and the interior and defense ministers, saying they are compromised by close relationships with the former president.

Also Monday, the top U.S. envoy for the Middle East, Jeffrey Feltman, arrived in Tunis to meet with members of the interim government. Assistant Secretary of State Feltman was discussing plans for "democratic reforms and elections," the State Department said.