Israel-Gaza updates: Israeli forces preparing for 'wide range of offensive plans'

In the wake of Hamas' attack on Israel, Israeli Prime Minister Benjamin Netanyahu on Monday said, "I call on the opposition leaders to immediately establish a national emergency government without preconditions."

"The people are united, and now the leadership needs to unite," he said, translated from Hebrew.

Netanyahu said Israeli's strikes on Hamas "have only begun."

"We have eliminated many hundreds of terrorists and we will not stop there," he said.

The prime minister said he's in constant contact with President Joe Biden and thanked the U.S. leader for his words and action.

He said "an American aircraft carrier, one of the largest in the world, is on its way to our region."

-ABC News' Will Gretsky

Itay Chen, a 19-year-old American citizen and Israel Defense Forces soldier, was at his IDF base at the Gaza border before he went missing over the weekend, according to his father, Ruby Chen.

"We got a message from him Saturday morning, 6:30 a.m., saying that there is bombing," Ruby Chen told ABC News. "That was the last time that we had any communication with him. Since then, he has been defined officially by the IDF as missing in action."

"My son, a U.S. citizen, is most likely in Gaza as we speak," he said.

7:08

Father of missing Israeli soldier pleads for his return Ruby Chen, the father of a U.S. citizen who is an IDF soldier, pleads for his son’s return after being classified missing in action.

ABCNews.com

The terrified father is pleading for action.

"There are multiple U.S.-Israeli citizens that are in the same situation as we are," he said. "What we are asking from President Biden, in addition to condemning, is being more vicious in his request from the Hamas to abide to international law when it comes to [prisoners of war]. That means that they need to identify each POW that they have. It means that they need to provide and take care of their health and they need to allow the U.N. … to come and visit those prisoners of war."

"Please help me," he said.

-ABC News' Michelle Stoddart

Hamas said the group will start killing Israeli hostages one by one and film the executions unless Israel immediately stops shelling homes in Gaza, or provides warning ahead of attacks.

Israeli officials said at least 100 civilians and soldiers have been taken hostage by Hamas. The Israel Defense Forces said it's obtained information on every Israeli kidnapped and that it has notified 30 families so far.

The Israel death toll has climbed over 900 since Saturday, with more than 2,500 others injured, according to the Israeli Health Ministry.