Anti-corruption authorities unveiled charges this week against several senior security and law enforcement officials over their alleged role in shielding a vast criminal ring.
Investigators said the group ran scam centres, traded drugs and produced fake currency and cigarettes with the help of top employees from the SBU security service, National Police and Prosecutor General's office.
Some had helped plan kidnappings and other forms of violence for the ring.
In his evening address, Zelenskiy said the alleged crimes - part of an evolving probe by the National Anti-Corruption Bureau of Ukraine and its sister agency - were "frankly shameful, absolutely unacceptable".
The investigation was the latest high-profile case against sitting officials that has angered many people fighting for survival as Russia continues to wage war in Ukraine.
"There have already been dismissals in the Security Service of Ukraine because of this, and there will be other personnel decisions," Zelenskiy said, adding that he expected a full investigation with results.
A Ukrainian court on Friday ordered the arrest pending bail of a former SBU general in connection with the case.
Two police officials and another suspect were also ordered held this week.
Zelenskiy said he had proposed new legislation requiring all employees of the SBU, which enjoys sweeping law enforcement and military powers, to publicly declare their assets.
Asset declarations have been a powerful tool for monitoring corruption in Ukraine, which must eradicate graft to secure membership in the European Union and continue receiving badly needed financial aid.
The SBU's military wing carries out long-range attacks on Russia and other daring wartime operations but other units have been hit by allegations of corruption and intimidation.
Ukrainian local officials said Russian forces hit energy infrastructure around the capital with missiles and drones on Saturday, straining Kyiv's power supply and heating systems as temperatures headed towards freezing point.
Three days before Russia and Ukraine are due to take part in US-brokered talks, explosions rocked Kyiv as Russia unleashed waves of ballistic missiles, several of which hit and damaged the Northern Bridge across the Dnipro River, Mayor Vitali Klitschko said.
Strikes on energy facilities outside Kyiv - including systems sending power from two nuclear plants to the city and Ukraine's central regions - caused serious damage, the energy ministry said.
Russia's defence ministry said it struck what it described as targets in Ukraine's military-industrial sector as well as energy and transport infrastructure in and around Kyiv.
