LVIV, Sept. 12 - Former Odessa governor Mikhail Saakashvili has been served legal notice by Ukrainian authorities after the stateless politician forced his way across the border from Poland, a move that puts him on a collision course with the government in Kyiv, AP reported.

Ukrainian border guards and police turned up at the hotel in the city of Lviv where Saakashvili was staying Tuesday and presented him with an official document detailing his alleged violation of crossing the border illegally.

Local media reported that the ex-Georgian president and former governor of Ukraine's Odessa region was ordered to appear at a court hearing over the incident on Monday.

The headstrong and divisive Saakashvili poses a challenge to Ukrainian President Petro Poroshenko, who once was his patron but revoked his Ukrainian citizenship in July. Surrounded by supporters, Saakashvili broke through a cordon of Ukrainian border guards at the Ukraine-Poland border Sunday.

But returning to Ukraine is also a risk for Saakashvili, who is stateless because he was forced to give up citizenship in his native Georgia when he received Ukrainian nationality.

"We are acting lawfully and protecting the law," Saakashvili said during an improvised press conference outside his hotel Monday that his supporters livestreamed. He announced plans to hold rallies in towns across Ukraine and to travel to the capital, Kiev.

Poroshenko has said that Saakashvili committed a crime by entering the country.

Ukraine's Interior Ministry said on Facebook Tuesday that five people who crossed into Ukraine from Poland with Saakashvili were arrested on criminal charges.

Saakashvili leads a small Ukrainian political party called the Movement of New Forces and has vowed to shake-up Ukrainian politics now that he is back in the country.

In an interview with The Associated Press at his hotel Monday night, Saakashvili called the current situation in Ukraine "tragic" and said he would devote himself to helping to create a "new political class for an emerging Ukraine."

"We need new people. Ukraine is fed up with old corrupt political class. They want new people, new energy, new faces, new ideas," he told the AP.

Saakashvili was appointed governor of Odessa in 2015 on the strength of his record of fighting corruption as Georgia's president between 2004 and 2013. However, he resigned from the Odessa post after 18 months, complaining that official corruption in Ukraine was so entrenched he couldn't work effectively.

It is "very important not to allow oligarchs to get away with an imitation of reform," Saakashvili said Sunday.

Georgia, where Saakashvili faces accusations of abuse of power and misappropriation of property, has sent an extradition request for him to Ukraine. It is not clear if Ukraine intends to honor the request. (ap/ez)