Israeli military spokesman Lieutenant Colonel Jonathan Conricus told reporters on Monday that the men "were inside Israeli territory but beyond the fence" separating the Israeli-occupied sector of the Golan Heights and the Syrian part of the territory.
He added that an Israeli commando unit, backed by airstrikes, fired simultaneously towards the men after 11 pm Sunday (2000 GMT).
"Our estimate is that all four were killed," Conricus said in the telephone briefing. According to the military, no Israeli casualties were reported.
There was no confirmation of the Israeli claim by any other party. The Israeli military did not link the men to any organization.
Israel has placed its forces near the border with Lebanon and Syria on high alert after Lebanon’s Hezbollah resistance movement announced the death of one of its members in an Israeli airstrike in Damascus on July 20 and promised retaliation.
Last week, Israeli and Western media outlets claimed that Israel's forces had thwarted an effort by Hezbollah fighters to infiltrate into the occupied territories through Shebaa farms along Lebanon’s southern border.
Last Monday, Hezbollah dismissed the claim about border clashes as fake, saying it was aimed to boost the morale of Israeli forces by fabricating fictitious victories.