According to Ukrinform, Poroshenko is on a working visit to Lithuania on December 8 to participate in the tenth meeting of the Council of Presidents of Ukraine and Lithuania.
Saakashvili resigned as mayor of Odessa after declaring he could not remain in the position due to corruption that President Poroshenko was sponsoring and enabling. The president, his former patron, rescinded his Ukrainian citizenship in July while he was out of the country.
The search of Saakashvili's home was conducted two days after his Movement of New Forces party organized a rally in Kyiv calling for Poroshenko's impeachment and for legislation that would allow it to take place.
"We are deeply concerned about recent attacks on independent anti-corruption institutions such as NABU and SAPO in Ukraine that threaten their ability to fight corruption and recover stolen assets", it said.
The Ukrainian authorities should ensure the independence of the National Anti-Corruption Bureau of Ukraine (NABU) and not interfere in its work.
Saakashvili supporters freed him from a police van after he was detained on Tuesday.
On Friday Poroshenko said he would soon introduce a draft law to set up such a court, taking into account recommendations by the Venice Commission, a leading European rights watchdog.
Saakashvili became a regional governor in Ukraine in 2015 at Poroshenko's invitation but they later fell out, with the former Georgian leader accusing the president of corruption.
Prosecutors, who say Mr Saakashvili is being funded by businessmen close to Russian Federation, released audio and video recordings which they say proved he had received hundreds of thousands of dollars from the criminal group. Saakashvili denies the charges against him.