World Bulletin/News Desk
The move appeared to increase the possibility of a split in the sprawling former Soviet republic of 46 million, despite denials by the leaders that this was their intention.
The Kiev parliament has passed a series of measures that would reduce the president's powers and pave the way to the formation of a national unity government and early presidential elections.
But a resolution adopted at the meeting said: "The decisions taken by the Ukrainian parliament in such circumstances cause doubts about their ... legitimacy and legality."
It added: "The central state organs are paralysed. Until the constitutional order and lawfulness are restored ... we have decided to take responsibility for safeguarding the constitutional order, legality, citizens' rights and their security on our territories."
One speaker urged the creation of civilian patrols to restore order. Another said those gathered should fear reprisals if anti-Yanukovich protesters in Kiev seize power in the whole of the country.
Yanukovich said he had no intention of quitting or leaving Ukraine and declared all moves taken by parliament on Saturday to be illegal and amounting to a "coup d'etat", Russian news agency Interfax reported, citing a television interview.
A day after Yanukovich signed an agreement with the opposition to relinquish some of his powers, his opponents were in control of the presidential administration and the Interior Ministry responsible for the police turned its back on him.
The regions represented at the meeting - Kharkiv, Donetsk, Dnipropetrovsk, Lugansk and Crimea - have a population of 14.4 million. Most are important industrial centres and Russia's Black Sea fleet is based in the Crimean port of Sevastopol.
TALK OF A SPLIT
Many politicians have warned of a looming partition in Ukraine, which broke peacefully from the Soviet Union in 1991, since people took to the streets late last year to protest against Yanukovich for spurning political and trade deals with the European Union. Western Ukraine is broadly pro-EU.
Some Ukrainians are also worried by calls in Crimea for the region to again become Russian territory, nearly six decades after Kremlin leader Nikita Khrushchev - who was a Ukrainian - redrew internal Soviet boundaries to make a gift of the peninsula to Ukraine.
"If Yanukovich appears and ... proclaims an alternative power in Kharkiv or in Donetsk - it will mean that we have two countries. The most serious risk now is the possible division of the country. The crisis is not yet over."
Russia has strong cultural, historical and economic ties with eastern Ukraine, and some factories there have contracts with the Russian military. Some Russians do not think of Ukraine, the cradle of Russian civilisation, as outside Russia.
"If there is stability anywhere in Ukraine right now, it's in those regions that are represented here today," he said.
This, he said, was in contrast to "western regions where buildings have been seized, where there are weapons, APCs (armoured vehicles) and the destruction of authority."
Andriy Sadovy, mayor of Lviv in the west, voiced concern that Ukraine could lose control of some of its territory and told a news conference: "We won't give up one centimetre of Ukrainian land to anyone."
Putin has made clear he does not want Ukraine to move out of what he considers Russia's sphere of influence, and agrement on a $15-billion Russian bailout plus a cut in how much Ukraine pays for Russian gas helped persuade Yanukovich to pull out of the planned deals with the EU at the last minute in November.
A Kremlin aide, Sergei Glazyev, has floated the idea that Ukraine could become a federation giving more power to its regions - a move, he said, that might enable eastern regions to join a trading bloc led by Russia.
That call has been taken up by parliamentarians in Moscow, fuelling speculation that this - or some form of annexation of Russian-speaking areas - may have the Kremlin's backing.