"My first decisive step will be aimed at ending the war, ending chaos, and bringing peace to a united and free Ukraine," Poroshenko (pictured above left) said at a press conference in Kyiv, with exit polls showing him a clear victor in Sunday's poll with almost 56 percent of the vote.
"The presidential election showed that Ukrainians have chosen the path of European integration," he added.
The exit poll results put 48-year-old Poroshenko - known as the "Chocolate King" - far ahead of his nearest rival, former Prime Minister Yulia Tymoshenko. If they are confirmed by election officials, a June 15 run-off will be rendered unnecessary.
Turnout was strong in the capital, Kyiv, and the west of the country, but voting was hindered across most of the east by pro-Russian separatists.
Poroshenko vowed to pay his first trip outside the capital to the eastern industrial belt, where the pro-Moscow insurgents have declared the creation of their own independent republic amid violence that has claimed more than 150 lives.
He also announced victory for boxing champion Vitali Klitschko (pictured above right) in Kyiv's mayoral election, with exit polls giving the heavyweight boxer turned opposition hero nearly 60 percent of the vote.
Klitschko had been in the running for the presidency, but dropped out of the race in March to support Poroshenko.
Sunday's ballot was called after pro-Kremlin President Viktor Yanukovych was ousted in February following months of protests sparked by his rejection of an Association Agreement with the European Union in favor of closer ties with Moscow.
Since his ouster, Russia has annexed Ukraine's Crimean Peninsula and vowed to "protect" the country's ethnic Russian community from alleged mistreatment.
However, Russian President Vladimir Putin, who is facing the threat of more US and EU sanctions for his actions, said on Friday he would be ready to work with a new government in Kyiv.
"We understand that the people of Ukraine want their country to emerge from this crisis. We will treat their choice with respect," he said.
Ukrainian authorities had mobilized 100,000 police volunteers to ensure security during the vote, but no violence was reported.
On Saturday, however, an Italian photographer and his Russian translator were killed after being caught in a gun battle.
tj/dr (AFP, dpa, Reuters)