MOSCOW — Mikheil Saakashvili, the former president of Georgia, was arrested on Friday in Ukraine during a late-night police raid on an apartment where he had been hiding after his escape from custody following a rooftop struggle with security agents this week.

Yuriy Lutsenko, Ukraine’s prosecutor general, said in a Facebook post that Mr. Saakashvili, the standard-bearer of a vociferous campaign to remove the president of Ukraine, Petro O. Poroshenko, had been seized late Friday by police officers in the Ukrainian capital, Kiev, and placed in a pretrial detention center.

Scores of Mr. Saakashvili’s supporters gathered overnight outside the detention center, which is operated by the domestic security agency, and chanted “glory to Ukraine” and other slogans. Vowing to stay until Mr. Saakashvili was released, they lit fires in the street to keep warm, just as protesters did in the winter of 2013-14 during an ultimately successful campaign to oust Ukraine’s previous president, Viktor F. Yanukovych.

A few hours before he was detained, Mr. Saakashvili had called for weekend protests against Mr. Poroshenko in Independence Square, an area in Kiev known as Maidan that was the center of the earlier demonstrations against Mr. Yanukovych.