Ukraine imposed sanctions on former president and opposition politician Petro Poroshenko, including an asset freeze and a ban on withdrawing capital from the country, for what the domestic spy agency said on Thursday were "national security" reasons.

Ukraine has announced sanctions on former president Petro Poroshenko and four other oligarchs and political figures accused of undermining national security, including a close ally of Russian President Vladimir Putin.

President Volodymyr Zelensky on Thursday signed off on sanctions against former Ukrainian President Petro Poroshenko and other prominent Russia-leaning officials.