Nationalist demonstrators on Saturday also attacked the offices of two Russian banks, throwing rocks at the windows and damaging furniture and equipment.
US Vice President Joe Biden praised the "brave Ukrainians" who took part in the protests as he held talks overnight separately with Poroshenko and Prime Minister Arseniy Yatsenyuk.
Biden said he stressed to both that "there is still a great deal of work to be done to honor the legacy of the brave Ukrainians who have given so much in their pursuit of a better future for their country".
German Foreign Minister Frank-Walter Steinmeier and his French counterpart Jean-Marc Ayrault are to travel to Kiev on Monday as part of a European bid to help ease the political crisis in Ukraine. The two ministers plan to hold meetings with Poroshenko, Yatsenyuk and former prime minister Yulia Tymoshenko, the German Foreign Ministry said.
`A third Maidan is possible`
Hundreds of people in Kiev headed to the city`s landmark Independence Square where the protests took place. They laid flowers and shared their grief as well as venting their frustrations with the current leadership.
"Of course, we are disappointed with many things, but there is still hope", remarked a woman named Tetyana. "Something is changing -- slowly, but it`s happening and that is already a victory", she said, wearing a yellow and blue Ukrainian flag draped on her shoulders.
Another elderly man carrying the red and black flag of the Ukrainian nationalist movement was more critical in his views of the current administration.
"If our government does not change its attitude to the situation, we will have to take some radical steps", he said. "A third Maidan is always possible. People realized that they can bring anyone to power and topple them at any time. The people realized they are strong."
Following the fall of the Russian-friendly regime, Russia annexed the Crimea and spawned an armed conflict in the east. More than 9,000 people have been killed and 20,000 injured since the crisis erupted in April 2014, according to the United Nations.