Police arrest more than 200 people outside the Brazilian embassy in the Honduran capital where Zelaya sought refuge this week when he entered the country, El Heraldo newspaper reported.
The Honduran leader was arrested and deported in June after a dispute over his bid to hold a referendum that would have allowed him to remain in office beyond the end of his term in January. Zelaya was replaced by interim President Roberto Micheletti in what Zelaya labeled a coup and Tegucigalpa officials called a legal response.
The United Stated called on all parties "to remain calm and avoid actions that might provoke violence in Honduras and place individuals at risk or harm," the U.S. State Department said in a statement.
"Above all, we stress the need for dialogue," State Department spokesman Ian Kelly read from the statement.
The United States also urged all parties to respect "the inviolability of the embassy of Brazil in Tegucigalpa and the individuals on its premises."
Kelly confirmed that water and electricity to the Brazilian embassy were cut off.
U.S. officials in Tegucigalpa have been in contact with their Brazilian counterparts, Kelly said during a news briefing in Washington.
"(We're) discussing what kind of assistance that we can ... provide to help them during this ... crisis," Kelly said. "It's a very sensitive situation there on the ground."