Russian passports have been distributed in the city of Mariupol in eastern Ukraine that had been taken under control by Russian forces earlier this month, Petro Andryushchenko, an advisor to the mayor of Mariupol, said on Wednesday.

"The de facto annexation of Mariupol, in particular, has begun," Andryushchenko wrote on Facebook.

Earlier in the day, Russian President Vladimir Putin signed an order allowing residents of Ukraine's southern Zaporizhzhia and Kherson regions to apply for Russian citizenship under a fast-track procedure, according to media reports.