Secretary of State Antony Blinken and Israeli Prime Minister Benjamin Netanyahu sheltered in a bunker for five minutes with the war cabinet and the rest of their meeting participants after rocket sirens went off in Tel Aviv on Monday, according to State Department spokesperson Matt Miller.

The meeting has since been moved and participants are going to an Israel Defense Forces command center to continue their discussions, Miller said.

Blinken returned to Israel on Monday to meet with Netanyahu. Miller said earlier that Blinken discussed in their meeting his "firm support" of Israel's right to defend itself and efforts to provide humanitarian aid and free hostages.

-ABC News' Shannon Crawford

The Pentagon has placed about 2,000 American troops on a heightened state of readiness to possibly deploy to the Middle East if they're needed, a U.S. official confirmed. The Wall Street Journal first reported the news.

If these units are deployed, their purpose would be to serve as a deterrent.

-ABC News' Luis Martinez

The Israeli hostages in Gaza include an elderly women with Parkinson's disease, a 60-year-old man with multiple sclerosis and children with autism, according to the Israeli Hostages and Missing Families Forum.

Other hostages are suffering from amputated limbs and severe injuries from rape, the group said.

The hostages are "enduring extreme conditions as time runs critically short," the group said.

The International Committee of the Red Cross said its met with Hamas leadership and is pushing Hamas for immediate release of the hostages.

The Red Cross is also asking Hamas to allow access to the hostages to provide care and to permit hostages to communicate with their families.

-ABC News' Will Gretsky

An Israeli airstrike struck a road close to the Rafah border crossing and also hit a nearby United Nations Relief and Works Agency warehouse, according to an Egyptian military source.

This is the fourth strike near the border since the war began.

Hamas fighters are believed to be "still hiding" in some communities in southern Israel even after the Israeli military took back control, according to Israel Defense Forces spokesman Maj. Doron Spielman.

"We are in control of the communities, but we actually assume that there are Hamas terrorists that are still hiding in these areas, including in the road where we are now," Spielman told ABC News during an interview Monday in Sderot, Israel. "In all these communities, we've seen terrorist come out of hiding. Just yesterday, they took over an ambulance."

"We're still being very, very careful," he added. "This is a war zone with active terrorists that are operating here."

Sderot is a southwestern Israeli city located near the county's border with the Hamas-ruled Gaza Strip. A police station there was stormed by Hamas fighters on Saturday as part of the militant group's wider incursion, leaving at least six Israeli police officers dead. The IDF then bombed the police station with the Hamas fighters inside, demolishing it.

Hamas fighters and other Palestinian militants are "striking strategic locations" along the border fence, allowing them to drive through in pickup trucks, Spielman said. Civilians in some of the local communities have been ordered to evacuate, while others have left voluntarily, according to Spielman.

"We do have a lot of ground troops in this area. We have a lot of tanks. We have, in addition, artillery. And we're prepared forever for anything," he said. "And if it happens, the next stage, it's going to happen here because this is the area that was the flashpoint and this is the area we're going to be presenting ourselves and finishing this battle. We, of course, have no choice but to finish."

When asked about the mounting casualties of Palestinian civilians in Gaza as a result of the IDF's retaliatory airstrikes, Spielman said: "We always try to avoid civilian casualties. However, I would say that this is war and our first priority here is to destroy Hamas."

-ABC News' Angus Hines and Ian Pannell