CAIRO (AP) — Egyptian prosecutors have ordered the detention for one day of an opposition leader widely tipped to challenge President Abdel-Fattah el-Sissi in 2018 elections following a complaint that he publicly made an obscene finger gesture.

Rights lawyer Khaled Ali, 44, unsuccessfully contested presidential elections in 2012. He did not run in the 2014 elections which el-Sissi won in a landslide, but told The Associated Press in February he was considering running next year.

One of his lawyers, Negad Borai, told the AP Ali was summoned by prosecutors on Tuesday for questioning in connection with the complaint, but refused to answer questions until he reviews evidence against him.

The incident allegedly took place outside a Cairo courtroom as Ali celebrated victory in a case he and other lawyers brought against the government.