Ukrainian President Viktor Yanukovych on Tuesday slammed opposition calls for revolution as a "threat to national security" when he met his predecessors in a bid to defuse an escalating standoff over a rejected EU pact. "Calls for a revolution pose a threat to national security," he told ex-leaders Leonid Kuchma, Leonid Kravchuk and Viktor Yushchenko in a landmark meeting. But in a nod to the opposition, he said he had asked the general prosecutor to secure the release of some of the demonstrators arrested after clashes with police. A senior delegation would also likely travel to Brussels for talks on an integration pact with the EU on Wednesday, Yanukovych added.