Togo's authorities are seeking opposition leader Harry Olympio in connection with an alleged attack on police headquarters last month.
The Olympios have a long feud with President Gnassingbe's family
Some of the 13 people arrested in connection with the petrol bomb attack have said they were working for Mr Olympio, the authorities say.
Mr Olympio has been in hiding since the attack but has denied involvement, saying he had fled death threats.
Mr Olympio ran against President Faure Gnassingbe in last year's elections.
His cousin Gilchrist Olympio heads another opposition party.
Harry Olympio's uncle, Sylvanus Olympio, was Togo's first leader before being ousted by Mr Gnassingbe's father, Gnassingbe Eyadema in 1963.
"The security forces are on the look out for Harry Olympio," Lome State Prosecutor Robert Boubadi Bakai told reporters on Monday.
There were no casualties or major damage in the firebomb attack.
Mr Olympio says he received anonymous calls, saying the security forces were going to kill him.
After last year's elections, thousands of opposition supporters fled Togo, saying they were being victimised by the security forces after violent protests over alleged poll fraud.