MOSCOW (REUTERS) - Russian Foreign Ministry Sergei Lavrov said on Monday Ukraine's Russian-speaking eastern regions should be involved in drafting a new state structure that Kiev has said may be put to a referendum next month.

Lavrov said it was not in Russia's interests for Ukraine to break up, but that Moscow wanted Kiev to give all citizens equal treatment.

He denied Ukrainian and US allegations that Russia had undercover agents fomenting unrest in eastern Ukraine, and said he was seeking an explanation of media reports that the director of the CIA, John Brennan, had visited Kiev.

Pro-Russian groups in eastern Ukraine have said they want a new constitution which will create a federal system of government with greater autonomy for the regions.

"I do not yet know the details of the referendum that has been announced for May 25," Lavrov said. He was speaking at a news conference after meeting his Sudanese counterpart.

"Fashioning some kind of text with the Verkhovny Rada (Ukrainian parliament) without the participation of the regions and then putting it to a referendum: that does not respond to the criteria we speak about or that the south east (of Ukraine) has spoken about and we back their stance."

"Let every political actor and every region without exception voice its interests and based on that we will look for a common denominator and then we will get a constitution that really unites and guarantees the interest of the people."

Responding to accusations from Kiev and some Western powers that Russia is preparing a military intervention in eastern Ukraine, Lavrov said: "As for your hypothetical question about ... possible military intervention, I don't even want to speculate. We do not meddle in the affairs of Ukraine."

"We don't have any agents there, not from the GRU (military intelligence) or the FSB (domestic security service)," Lavrov said, adding that it is "not in Russia's interest to destabilise the situation in Ukraine".