The 35-member Organisation of American States, or OAS, has given Honduras until Saturday to ensure that Zelaya returns to office.
Failure by the military-backed interim government to meet the deadline would trigger sanctions that could block international aid to the nation of 7.2 million people.
Separately, Sweden's foreign minister said that all ambassadors from European Union member countries had been recalled from the country.
"All EU ambassadors have now left [Honduras]," Carl Bildt, whose country is president of the 27-nation bloc, said in a blog on Thursday.
"The uncertainty about the developments in Honduras remains considerable."
Mariana Sanchez, Al Jazeera's correspondent, said that about 200 supporters of Zelaya had gathered in Tegucigalpa, the Honduran capital, on Thursday.
But while the city has been calm over the last few hours, the protesters told her that the authorities have sought to limit their movements and disrupt the opposition to the military-backed interim government.
|Honduran police have been granted powers by congress to move against the opposition [AFP]
"They say they were not allowed to gather at the plaza, where they wanted to be," she said.
"They also complained that the security forces are not allowing people from outside the capital to join the protests."
The apparent police pressure against Zelaya's supporters follows a vote by the legislature on Wednesday granting police expanded powers.
The Honduran congress passed laws allowing police to arrest people in their own homes without a warrant during a nightly curfew that has been in place since Zelaya was ousted and forced into exile.
"The deputies have decided to suspend several liberties, among them the liberties of free movement and association - people can be arrested for 24 hours without having any rights," our correspondent said.
Zelaya has promised to return to Honduras after the OAS deadline expires.
But Roberto Micheletti, the interim president, has vowed not to resign, saying that Zelaya will be arrested if he enters the country.
Supporters of both Zelaya and the interim government have each demonstrated in cities across Honduras since Zelaya was forced out of the country on Sunday.
Micheletti has said that Zelaya was not ousted through a coup but through "a completely legal process as set out in our laws", calling the move an "act of democracy".
Zelaya was removed from power as he was about to press ahead with a non-binding referendum on constitutional change on Sunday.
Congress and the courts had declared the move to hold the public vote illegal, accusing Zelaya of trying to change the charter to enable him to run for a second term in office.
Micheletti's government has also accused Zelaya of involvement in a drugs ring.
The US has not legally classified the removal of Zelaya as a coup, as this would automatically lead to the suspension of aid to Honduras, an impoverished nation of 7.2 million people.
But the Pentagon on Wednesday suspended joint military activities with Tegucigalpa until further notice.