Updated

Egyptian prosecutors on Tuesday 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 made an obscene finger gesture on the street outside a Cairo courtroom in January, according to one of his lawyers.

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.

Lawyer Negad Borai told the AP that Ali was summoned by prosecutors for questioning in connection with the complaint, but he refused to answer questions until he reviewed evidence brought against him. Ali was ordered detained until Wednesday when he would be shown the evidence, including a video clip, according to Borai, who was among several lawyers who accompanied Ali to the prosecution's offices.

Ali, a key figure among the small but vibrant core of mostly young pro-democracy and secular activists known loosely as the "revolutionaries," would spend the night at a police station, Borai added.

Although Ali's 2018 candidacy would be a long shot, it would win the support of hundreds of thousands of young Egyptian men and women who participated in the 2011 uprising that toppled autocrat Hosni Mubarak but who are now vilified by pro-government media as foreign agents and saboteurs. It may also win support among the millions of poor and middle-class Egyptians crushed by the steep rise in prices and services as a result of el-Sissi's ambitious economic reforms.

Ali sees his candidacy as a way to breathe some life into Egypt's leftist, revolutionary and pro-democratic forces after years of defeat and disarray under a massive crackdown overseen by el-Sissi that mostly targeted Islamists but also secular activists. As defense minister, el-Sissi led the military's 2013 ouster of the Islamist Mohammed Morsi, Egypt's first freely elected president whose one-year rule proved divisive.

It is not immediately clear why Ali was summoned for questioning over an incident that took place four months ago, but it followed the arrest of a yet undetermined number of young supporters preparing for his possible presidential bid and canvassing support for Bread and Freedom, the party he has recently founded and which awaits official registration.

The incident allegedly took place in January outside a Nile-side Cairo courtroom as Ali, carried on the shoulders of supporters, celebrated victory in a case he and other lawyers brought against el-Sissi's government. The ruling that day upheld a verdict by a lower court that repealed an agreement under which the Egyptian government was to hand over to Saudi Arabia two islands at the mouth of the Red Sea's Gulf of Aqaba.

The government contends the strategic islands of Tiran and Sanafir belong to the Saudis who placed them in Egyptian custody in the 1950s because they feared Israel would capture them. The agreement sparked the largest anti-government demonstrations since el-Sissi took office in June 2014.