Moscow on Wednesday ruled out intervening in Ukraine, where pro-Russian protesters in the Crimean peninsula are questioning the legitimacy of the new officials in Kiev.

"Russia has stated and insists on its position that we do not have a right and cannot intervene in the internal affairs of a sovereign state," Russian Senate President Valentina Matviyenko said.

Matviyenko's comments on the situation coincided with those of three former Ukrainian presidents - Leonid Kravchuk, Leonid Kuchma and Viktor Yushchenko - who said Russia was meddling in Ukraine's internal affairs, especially in Crimea, a peninsula on the northern coast of the Black Sea with a majority ethnic Russian population.

"Russia, which labels the efforts of our international partners to normalize the situation by peaceful means as 'interference' in Ukraine's internal affairs all the time, is now turning to direct interference in the political life of the Crimea," the three former presidents said in a joint statement.

Russian President Vladimir Putin, meanwhile, ordered military units in western and central Ukraine placed on alert to check their combat readiness.

"In accordance with an order from the president of Russia, troops have been placed on alert as of 1400 hours (1000 GMT) today," Defense Minister Sergey Shoygu told the Interfax news agency.

Airborne troops and air transport units are among those placed on alert, Shoygu said.

"The supreme commander has given the mission of confirming the combat readiness of troops for dealing with crisis situations that represent a threat to the country," the defense minister said.

Ukraine's crisis erupted at the end of November, when ousted President Viktor Yanukovych backed away from plans to ink a pact with the European Union and instead signed a $15 billion financial-aid package with Russia.

Protesters took to the streets of Kiev and began occupying administrative buildings, prompting Ukraine's parliament, then controlled by Yanukovych's allies, to pass a package of laws on Jan. 16 restricting freedom of assembly, freedom of speech and other basic rights.

Violent clashes pitting demonstrators and riot police broke out three days later and left six dead and hundreds wounded.

Ukrainian officials and opposition leaders began seeking a negotiated solution to the crisis in the wake of the bloodshed.

The talks led to the resignation of Prime Minister Mykola Azarov and the repeal of the controversial anti-protest laws, as well as the ouster of Yanukovych, whose whereabouts is unknown. EFE