LVIV, Ukraine (Reuters) - Ukrainian President Volodymyr Zelenskiy on Tuesday said the signals from peace talks with Russia could be called positive but added that they did not drown out the explosions from Russian shells.

       In a late night address, Zelenskiy also expressed caution about Russia's promise to sharply curtail military action in some areas and said Ukraine would not be easing off its defensive efforts.

       Russia and Ukraine have been holding peace negotiations in an Istanbul palace. Zelenskiy said Kyiv saw no reason to believe in words from some Russian representatives.

       "We can say the signals we are receiving from the talks are positive but they do not drown out the explosions of Russian shells," he said, adding that Ukraine could only trust a concrete result from the talks.

       Earlier in the day, Russia promised to scale down military operations around Ukraine's capital and north.

       Zelenskiy said that despite this vow, "the situation has not become easier ... the Russian army still has significant potential to continue attacks against our state." He added: "Therefore we are not reducing our defensive efforts."

       Zelenskiy reiterated that for any peace deal to work, Russian troops would have to leave and there could be no compromise on Ukraine's sovereignty and territorial integrity.

       He also called for tougher sanctions against Russia and ruled out the idea of current punitive measures being lifted until the war was over and justice had been restored.

       (Reporting by David Ljunggren and Ron Popeski; editing by Jonathan Oatis and Cynthia Ostererman)