Russian President Vladimir Putin arrived in Kiev on Saturday for politically charged festivities celebrating the arrival of Christianity in Russia and Ukraine, highlighting a tug-of-war over Kiev's moves to integrate with the EU.
The 1025th anniversary of Christianity in what was once known as Kievan Rus comes ahead of a November summit in Vilnius which could see the European Union sign a long-delayed association agreement with Ukraine.
Accompanied by Patriarch Kirill, the Russian leader and his host Viktor Yanukovych took part in a prayer service in central Kiev, the first item on Putin's agenda bulging with events designed to play up historic ties between the two majority Orthodox nations.
The two leaders are also scheduled to meet Ukraine's top Orthodox clerics and visit the country's main cathedral, the Kiev-Pecherskaya Lavra.
Ahead of the arrival of the top guests including the Serbian and Moldovan presidents, authorities in Kiev dramatically beefed up a police presence and sealed off access to the park where the prayer service was conducted.
Overlooking the Dnipro River, the park hosts a monument to Prince Vladimir the Great revered for converting ancient Rus to Christianity in 988.
Around 100 representatives of the ultra-nationalist party Svoboda (Freedom) and other nationalist groups staged a rally not far from the park protesting Putin's arrival.
The protesters held placards deriding the Russian strongman while police looked on.
Since coming to power in 2010, Ukraine's Yanukovych has performed a tight balancing act by seeking closer European ties while also trying to remain on good terms with prickly Soviet-era master Moscow.
Putin's spokesman Dmitry Peskov said closer cooperation would be discussed although no agreements would be signed.
"Issues linked to integration are certainly on the agenda of bilateral ties," he told AFP.
Fyodor Lukyanov, chairman of the Moscow-based Council on Foreign and Defence Policy, said the outcome of talks during the visit was expected to shape the future of bilateral ties.
"The closer the Eastern Partnership summit where Ukraine will supposedly sign the free trade agreement, the more interest in this topic and negative feelings come from Russia," Lukyanov said.
Kiev-based political analyst Oleksiy Haran said there were "deep contradictions" between Moscow and Kiev.
"Obviously, Putin will put pressure on Yanukovych, will try to dissuade him from signing the association agreement with the EU," he said.
The signing of the agreement has been repeatedly postponed after a Ukraine court jailed former prime minister Yulia Tymoshenko for seven years in 2011, triggering a dramatic deterioration in ties and making Kiev more vulnerable to Kremlin's advances.
Russia has sought to keep Ukraine in its orbit by exploiting Kiev's differences with the West and inviting the ex-Soviet neighbour to join the Moscow-led customs union.
Kiev has steadfastly resisted pressure from Moscow which wants to gain control of Ukraine's gas pipeline network in exchange for cheaper gas.
Repeated haggling over prices has led to interruptions of gas supplies to Europe, most notably in 2009 when Russia turned off the taps to Ukraine in the dead of winter.
On Sunday, Putin visits the Ukrainian port of Sevastopol, which hosts a Russian naval base, for joint celebrations of Navy Day.