The decision by Togo's opposition presidential candidate Bob Akitani to declare himself president has been criticised by the regional body Ecowas.
Mr Akitani claims he won 70% of the vote
Mr Akitani said he could prove he won more votes than official winner Faure Gnassingbe, the former leader's son.
But the interim president said Mr Akitani's move was unlawful and ordered the arrest of anyone breaking the law.
Ecowas called for a national unity government to prevent further violence, in which 20 people have died.
Street battles erupted after the provisional polls results were declared on Tuesday giving Mr Akitani - the main UFC opposition candidate - 38% of votes cast compared to 60% for the ruling RPT party candidate Mr Faure.
The United States said the poll fell short of expectations but Ecowas has given the poll a clean bill of health.
Interim President Abass Bonfoh said Mr Akitani's victory claim was "fantastical and unlawful".
"Those who violate the laws of the republic will be prosecuted and will be subjected to the rigours of the law," he said in a statement on state media on Wednesday night.
Ecowas Secretary-General Mohammed ibn Chambas said Mr Akitani's presidential declaration was "unacceptable" and he called on both parties to seek dialogue.
"The way forward is for both sides to work together. You cannot resolve the problems of Togo through unilateral action," he told the BBC's Focus on Africa programme.
"We urge those who believe in democracy to respect the constitution and the laws of the land."
Mr Atikani's coalition intends to appeal to Togo's constitutional court - which has still to confirm the result of the election - saying he won majorities in all the most populous regions of the country.
Faure Gnassingbe: 1.4m votes (60%)
Bob Akitani: 841,000 (38%)
Source: Electoral Commission (Provisional results)
His support is strongest in the south, including Lome, while Mr Faure's power base is in the north.
The BBC's Mark Dummett in the capital Lome said the city was calm on Thursday morning and security have been beefed up following two days of clashes between security forces and opposition supporters angered at the poll results.
Some 600 people are reported to have fled into Benin from southern Togo, following clashes in the town of Aneho.
Communication in the country is difficult, our correspondent says, as telephone networks are not working.
The local relay of Radio France Internationale and most of Togo's private radio stations were taken off the air on Wednesday.
Mr Faure denied vote-rigging and urged veteran opposition UFC leader Gilchrist Olympio to join a government of national unity.
Earlier, Mr Olympio, who was ineligible to stand in the poll because he lives in exile following a 1992 assassination attempt, said his party would not serve as a minority partner in any unity government.
The army tried to install Mr Faure after his father's President Gnassingbe Eyadema's death, but pressure led him to step down and call an election.
President Eyadema, who Togo for 38 years, had seized power in a coup from Mr Olympio's father, Sylvanus, in 1963.