"Like every day... the children were spending their day playing," said Jarkas, 55, a farm worker originally from north Syria's Afrin area but now living in the southern border village of Umm Toot.
"I heard the sound of a strike" and ran towards it, he said.
Jarkas said he found his children, Jean, 10, and Mohammed, seven, "drowning in blood".
Lebanese official media said separate Israeli strikes on Tuesday in south Lebanon, including on Umm Toot, killed five Syrians, three of them children, with Hezbollah announcing rocket fire at Israel in retaliation.
The Iran-backed group has traded almost daily fire with Israeli forces in support of its ally Hamas since the Palestinian militant group's October 7 attack on Israel triggered the war in the Gaza Strip.
The Israeli military said on Tuesday that its air force struck "a Hezbollah terrorist cell" in the Yarin area, near Umm Toot, releasing a video of the strike.
On Wednesday, the children's bodies, wrapped in what appeared to be bed coverings, were laid out on stretchers as mourners gathered and a sheikh led funerary prayers.
Another Syrian agricultural worker in Umm Toot, Mohammed Khalil, 58, said at first he didn't know where exactly the strike had hit.
"We ran to check on the children who had been playing," he said, his face gaunt and his hair grey.
"We found them dead," with his 12-year-old son Khalil Khalil among them, he said.
Around him in Qasimiya in the Tyre district, where the bodies were taken for funerals, people wept, women screamed in grief, and some embraced and consoled each other.
"We came as refugees from (Syria) in order to protect our children," he said.
"The Israeli government is responsible" for their killing, he added.
United Nations children's agency UNICEF on Tuesday called the children's deaths "horrific".
Hezbollah leader Hassan Nasrallah warned on Wednesday that his fighters would hit new targets in Israel if more civilians were killed in Israeli strikes on Lebanon.
The cross-border violence since October has killed 511 people in Lebanon, mostly fighters but also including at least 104 civilians, according to an AFP tally.
On the Israeli side, 17 soldiers and 13 civilians have been killed, according to authorities.
The violence, largely restricted to the border area, has raised fears of all-out conflict between the two foes, who last went to war in the summer of 2006.
