According to the assessments of police, which has been ensuring public security during the rally, the march has gathered several thousand individuals.
The rally was expected to start at noon local time (10:00 GMT), however it has been delayed by 50 minutes. The organizers of the march cited the delays of public transport operation in Ukraine, preventing the rally participants from arriving in central Kiev on time.
Saakashvili is not attending the march since he was deported by the Ukrainian authorities to Poland on Monday.
The march is headed by the members of Saakashvili’s Movement of New Forces party.
The demonstrators are holding the Ukrainian national flags and flags of Ukrainian nationalists. They chant slogans calling for Poroshenko to step down, and urge the Ukrainian authorities to take their "hands off" Saakashvili.
The rally's participants are also demanding the snap election to the Ukrainian parliament and forming the new government.
The march’s bill reads that the parliament should include "300 new lawmakers, who will be independent from any political forces and oligarchs, with one year term of office."
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Individuals, holding plastic boxes for collecting money in support of Saakashvili, are moving among the protesters.
After marching along Kiev’s central Volodymyrska street to Mykhailivska Square, the group started a congress, referred to in Ukraine as veche, in support of Poroshenko’s resignation.
The situation in central Kiev is calm.
Sunday marks the fourth anniversary of the February 2014 violent clashes between protesters and law enforcement in Kiev, commonly referred to as the Euromaidan, after which Poroshenko came to power.
On Monday, Saakashvili was deported from Ukraine to Poland from where he had illegally entered Ukraine in September.
Over the recent months, Saakashvili has been leading anti-government rallies in Kiev, calling for the impeachment of Poroshenko and well as for the introduction of legislation to fight corruption in the country.