Russian President Vladimir Putin (R) shakes hands with his Turkish counterpart Tayyip Erdogan after the talks at the Kremlin in Moscow, Russia, March 10, 2017. REUTERS/Alexander Zemlianichenko/Pool

ANKARA (Reuters) - Russian President Vladimir Putin has called his Turkish counterpart Tayyip Erdogan and congratulated him for winning the referendum, Turkish presidential sources said on Tuesday.

The two leaders discussed ramping up efforts to normalize ties and highlighted the importance of working together to strengthen the ceasefire in Syria.