Assistant Minister Damir Kusen handed the note to Ambassador Radivoje Cveticanin in which the Croatian side harshly protested against the assault and demanded a complete report on what was being done.
Croatia said in the note it expected the perpetrators to be found and punished as soon as possible and wanted guarantees for the safety of the Croatian Embassy staff in Belgrade.
Cveticanin expressed regret over the incident, voicing conviction that everything would be done to find and punish the culprits.
The two diplomats were physically assaulted on Wednesday evening in the Senjak neighbourhood, where the residences of a number of diplomats are located, Serbian Interior Ministry spokeswoman Dragana Kajganic told Hina today.
Deputy Ambassador Branislav Loncar and first secretary Boris Herceg were attacked as they were sitting in a car with diplomatic licence plates. Four persons lunged at the vehicle, with one of them smashing a window and hitting Herceg, who was in the driver's seat and sustained light injuries.
Police arrived shortly after the incident but the attackers had fled, said Kajganic, adding that an intensive search for them was under way.
Speaking to the press in Budapest after a session of the Croatian and Hungarian governments, Croatian Prime Minister Ivo Sanader said he assumed this was an isolated incident which had no other political implications.