Interim President Roberto Micheletti has imposed an overnight curfew in Honduras, hours after being sworn in.
The Congress speaker took office after troops ousted elected leader Manuel Zelaya and flew him to Costa Rica.
The removal of Mr Zelaya came amid a power struggle over his plans for constitutional change.
Mr Zelaya, of the Liberal Party, who had been in office since 2006, wanted to hold a referendum that could have led to an extension of his non-renewable four-year term.
Polls for the referendum had been due to open early on Sunday - but troops instead took him from the presidential palace and flew him out of the country.
The ousting of Mr Zelaya has been criticised by regional neighbours, the United States and the United Nations.
Mr Micheletti told a news conference that a nationwide curfew was being imposed for Sunday and Monday, running from 9pm to 6am.
Many Hondurans say there is a total lack of information about what has happened to their country and their president, the BBC reports.
The swearing in of Mr Micheletti - constitutionally second in line for the presidency - was greeted with applause in Congress. In a speech, he said that he had not assumed power "under the ignominy of a coup d'etat".
The army had complied with the constitution, he said, and he had reached the presidency "as the result of an absolutely legal transition process".
Congress said he would serve until 27 January, when Mr Zelaya's term was due to expire. Presidential elections are planned for 29 November and Mr Micheletti promised these would go ahead.
Both Congress and the courts had opposed Mr Zelaya's referendum, which asked Hondurans to endorse a vote on unspecified constitutional changes alongside the November elections.
Tensions over the issue had been escalating for several days, with the army refusing to help with preparations for the referendum.
Just before dawn on Sunday, troops stormed the president's residence. There was confusion over his whereabouts for several hours before he turned up in Costa Rica.
