French President Nicolas Sarkozy brokered the deal to end August's brief war between Russia and Georgia, but analysts say tension on the de facto border between South Ossetia and undisputed Georgian territory could spark new fighting.
Russian troops this month pulled out of areas adjacent to South Ossetia and the second Georgian separatist region of Abkhazia in line with the ceasefire deal and allowed some 300 unarmed European Union observers and support staff in the area.
A South Ossetian official said EU monitors remained silent while Georgian forces fired at Ossetian villages.
"For a week now, Georgia has been shooting daily at the border districts of Znaur and Tskhinvali," Irina Gagloyeva, head of the separatist Press and Information Committee, told Reuters by telephone from South Ossetia's capital Tskhinvali.
"Georgia is violating the (French-brokered) agreement ... it has resumed its aggressive actions." She said separatist Interior Minister Mikhail Mindzayev had ordered "all security bodies to give an adequate response to all Georgian provocations".
"Accordingly, all Georgian firing positions will be destroyed," Gagloyeva said. "By the way, all this is happening in the presence of international monitors who -- quite surprisingly to us -- turn out to be blind, mute and deaf."
"We now have the impression the international community does not want to see stability here," she added.
Russia launched a massive counter-strike after Georgian forces tried to retake South Ossetia, a region that rejected Tbilisi's rule in a separatist war in the early 1990s.
Moscow says it acted to prevent greater bloodshed, but Western states condemned its response as disproportionate.
Russia has since recognized South Ossetia and Abkhazia, both pro-Moscow, as independent states.
Georgia, a close U.S. ally, accused the separatists of fanning tensions along the de facto frontier.
"This escalation plays right into the hands of those who do not want EU monitors to implement their mandate of monitoring in Abkhazia and South Ossetia," Georgian National Security Council Secretary Kakha Lomaia told Reuters by telephone from Brussels. "Such declarations are made by those unwilling to see the return of (Georgian) refugees to their homes. This only further whips up tension."
International negotiations in Geneva last week to establish a lasting security mechanism for Georgia collapsed after Moscow and Tbilisi could not agree on how the separatists should be represented at the talks.
"Russia will discuss this problem only if Abkhazian and South Ossetian representatives take part," said Russian Deputy Foreign Minister Grigory Karasin, Moscow's chief negotiator at the Geneva talks.
"Tbilisi wants to present it in such a way as if the August 7-8 aggression never happened," he said in an interview with Russia's Ogonyok weekly magazine published on Monday.
"They are proposing we start with a 'clean page', but unfortunately this page is already stained with blood and marked with human suffering."