BELGRADE, May 12 (Reuters) - Ukraine's first lady Olena Zelenska arrived in Belgrade on Sunday, the first visit by a top Ukrainian dignitary to Serbia since Russia's invasion in 2022 and a signal of the Balkan country's swing away from Moscow, its traditional ally.

Flanked by her Serbian counterpart Tamara Vucic and Ukraine's foreign minister Dmytro Kuleba, also on his first visit to Belgrade, Zelenska toured the city and its medieval Kalemegdan fortress, the Tanjug news agency reported.

She also attended the signing of an agreement on cooperation between universities in Belgrade and Kyiv, the report said.

Pro-Russian sentiments run high in Serbia on the back of traditional historical, religious, political, and military ties, but also due to Russian propaganda mainly focused on social networks and rightist groups.

Serbia has repeatedly condemned Russia's invasion in the United Nations and other international forums, but has so far refused to join international sanctions against the Kremlin.

Its President Aleksandar Vucic has met Ukraine's leader Volodymyr Zelenskiy three times since 2022 during international forums abroad, most recently at a regional meeting in Tirana in February.

Since 2022 Serbia has accepted thousands of Ukrainian refugees, sent humanitarian aid to Ukraine and pledged help in de-mining the country and in its post-war rebuilding effort.

Last year, a classified Pentagon document said Serbia has agreed to supply arms and ammunition to Kyiv or has sent them to Ukraine. (Reporting by Aleksandar Vasovic; Editing by Jan Harvey)