THE European and Ukrainian parliaments have voted to ratify a major EU-Ukraine association agreement that aims to bring the ex-Soviet republic closer to the EU.
Mr Poroshenko said the ratification of the EU deal marked a "historic day".
The EU-Ukraine agreement lies at the root of Ukraine's crisis. It was former President Viktor Yanukovych's refusal to sign the deal last November that triggered mass protests and his eventual fall from power.
Russian President Vladimir Putin has consistently railed against closer ties between the EU and the former Soviet republic.
The votes ratifying the agreement took place simultaneously, with a live video link-up between the parliaments in Strasbourg and Kiev.
Both President Poroshenko and the President of the European Parliament, Martin Schulz, called it a historic day. The agreement would make Ukraine compliant with EU standards in the areas of human rights, security and arms control, and would remove trade barriers. But negotiations with Russia last week led to the free-trade part of the agreement being postponed until 2016. Russia has said its market could be flooded with cheap EU goods shipped via Ukraine.
In Kiev yesterday tensions were running high and one MP Vitaly Zhuravsky was thrown into a bin by a mob angry at the EU deal.
In another major development, Ukrainian MPs granted self-rule to parts of two eastern regions, and an amnesty to pro-Russian rebels there. The law affecting Donetsk and Luhansk regions - which is in line with the September 5 ceasefire - was condemned by some MPs as "capitulation". Last night Mr Poroshenko stressed that the legislation giving the special status to parts of Donetsk and Luhansk regions for three-years would guarantee the "sovereignty, territorial integrity and independence" of Ukraine, while paving the way for decentralisation. Meanwhile, Russia threatened to send more troops to its newly-annexed territory of Crimea last night, after NATO began exercises in western Ukraine while Kiev's forces are fighting pro-Russian separatists in the east.
Defence Minister Sergei Shoigu said the escalation of tensions in Ukraine and the presence of foreign military near Russia's borders made the deployment of troops a top priority in Crimea, which Russia annexed from Ukraine in March.
"The situation has escalated sharply and the presence of foreign military has increased in the immediate vicinity of our borders," news agency Itar-Tass quoted Shoigu as telling military commanders.
"The deployment of proper and self-sufficient forces to Crimea is a top priority."
Unrest in Ukraine, which Kiev says is being fanned by Russian weapons and soldiers, has plunged ties between Russia and the West to their worst level since the end of the Cold War.
Moscow warned that NATO's Rapid Trident exercises, which will last until September 26 and involve more than 1,000 troops from the United States and its allies, threatened peace efforts in eastern Ukraine, including a fragile ceasefire.
NATO said Russia still had around 1,000 soldiers and hundreds of combat vehicles and artillery inside Ukraine, despite some cuts in troop numbers since the ceasefire began on September 5.
The Rapid Trident exercises, seen as a sign of the alliance's commitment to support non-member Ukraine, are to be held around Lviv near Ukraine's border with Poland, nearly 1,000km from the rebel stronghold of Donetsk in the east. NATO officials have said the bloc will not send "lethal assistance" to Ukraine, but member states may do so. Earlier this month, a senior Ukrainian official said Kiev had agreed on the provision of weapons and military advisers from several members of the US-led alliance. Four of the five countries named, including the United States, denied this.
Last night, Russian parliamentary speaker Sergei Naryshkin said shipments of weapons from NATO countries would "abet war crimes" in Ukraine, where Moscow accuses Kiev's forces of bombing residential areas.