TEL AVIV U.S. citizens living in Israel urged U.S. President Joe Biden to do what he could to help them reunite with loved ones missing since the weekend attack that saw Islamist Hamas gunmen rampage through Israeli towns and take hostages.

At a press conference, the family members shared stories of relatives who have not been heard from since Saturday, and their distress at not knowing their fate.

"When I turned (my phone) on, there were two texts in a row from Hersh at 8:11. The first one said, 'I love you,' and immediately at 8:11, also it said, 'I'm sorry,'" said the mother of Hersh Polin-Goldberg, who was at a dance party attacked by the militants.

"And so I knew immediately, wherever he was, it was a terrible situation. I took it to mean 'I love you and I'm sorry' because whatever is going to happen is going to cause you tremendous pain and worry," said Rachel Goldberg, who has not heard from her son since Saturday's text.

"Since that time, I, of course, tried calling him right back. There was no answer," she said.

The victims of the weekend attack were overwhelmingly civilians, gunned down in homes, on streets or at the outdoor dance party. Scores of Israelis and some foreigners were captured and taken to Gaza as hostages, some paraded through the streets.

In retaliation, Israel hammered the Gaza Strip on Tuesday with the fiercest air strikes in its 75-year conflict with the Palestinians.

Nahar Neta, the son of missing 66-year-old nurse Adrienne Neta, said: "It is a bit ridiculous at this stage to say, but the optimistic scenario here is that she's held hostage in Gaza and not dead on the street of the Kibbutz where we grew up."

Ruby Chen said his son Itay Chen - who was serving in the Israeli army near the Gaza border - has not been heard from since Saturday morning, when he told his family he was under attack.

"The U.S. has a lot of resources at its attention. It is able to do many things that can be different than what the Israeli government could do. And we are asking, on behalf of my family for President Biden... and (the) Secretary of State to do what they can to make this end for us as soon as possible."

On Tuesday, Biden is set to make a speech in which he will condemn Hamas and express concern about the potential that some Americans are being held hostage by Hamas, as well as outline military assistance being provided to Israel.

At least 11 Americans perished in Saturday's attack.

(Reporting by Mira Maman and Janis Laizans, Writing by Rosalba O'Brien, Editing by Nick Zieminski)