The Israeli government announced Wednesday there will be 50,000 additional reserve soldiers in preparation for possible escalation on the Lebanon front.

The announcement, made on Israeli Army Radio, came on the same day as Israeli Prime Minister Benjamin Netanyahu's visit to the northern border.

Netanyahu said Israel is "prepared for a very strong action in the north."

-ABC News' Ellie Kaufman

At least 18 suspects were arrested on suspicion of "violent crimes, assault and threats and disorderly conduct at the annual march to mark Jerusalem Day," according to Israeli Police.

The march of flags continues into the Old City and the Western Wall as thousands of Jerusalem District police officers, police reinforcements, MGB fighters and volunteers work in the various missions and sectors. The Israeli Police said it is working throughout Jerusalem to secure the tens of thousands of participants, maintain order and direct traffic on Jerusalem Day.

The march left a trail of violence as it kicked off in the early afternoon of Wednesday. Predominantly right-wing Israeli ultra-nationalists attended, many very young, marching through Muslim areas of Jerusalem’s Old City and attacking local business owners and journalists.

Among those arrested were suspects of different ages involved in “various incidents of violence in the Old City, possession of a knife and threats towards police officers,” police said.

Some of the roads that were blocked were opened to traffic and the police continue to work to maintain security and order.

Al-Asima journalist Saif Al Qawasmi said he was attacked on duty and beaten on his head and hand, video shows.

Hareetz journalist Nir Hasson also said he was attacked by a group of Israeli nationalist youths and posted videos showing the violent scenes.

These protesters were consistently chanting racist slurs throughout their march and attacking people as filmed by witnesses and reported by an ABC News team on the ground.

The massive group of far-right Israelis marched into Jerusalem’s old city chanting, “Death to Arabs!” “May your village burn!” and “The nation is alive!"

Tensions were already high for this event, which draws thousands of people and all Palestinian shops were closed by the Israeli police.

-ABC News' Marcus Moore, Nasser Atta, Jordana Miller and Camila Alcini

Amid an escalation of fighting and bombing in Gaza, at least 70 are dead and over 300 wounded in the last 48 hours, according to Doctors Without Borders.

"We have seen hospitals being bombed. We have seen refugee camps being bombed. We have seen humanitarian warehouses being bombed. The situation is apocalyptic," Karin Huster, a Doctors Without Borders nurse, said in a statement Wednesday.

"While the Rafah crossing point remains closed, these repeated mass casualties incidents are bringing the health system to the point of collapse," Doctors Without Borders said in a statement.

Medical teams at Al-Aqsa hospital -- one of the only remaining functional health facilities in central Gaza -- have received a huge influx of patients, many of whom arrived with severe burns, shrapnel wounds, fractures and other traumatic injuries.

"The odor of blood in the hospital's emergency room this morning was unbearable. There are people lying everywhere, on the floor, outside... bodies were being brought in plastic bags. The situation is overwhelming," said Huster.

-ABC News’ Guy Davies

The U.S. continues to push Hamas to agree to the cease-fire proposal President Joe Biden outlined Friday, saying Hamas' stated opposition to the deal has yet to be officially transmitted.

"We've seen some public comments from Hamas officials, but we have not yet gotten an official response from Hamas to the Qataris, who are the mediator to whom Israel gave their proposal that was transmitted to Hamas," White House national security adviser Jake Sullivan told ABC's George Stephanopoulos on "Good Morning America" Wednesday.

"The ball is in Hamas's court," Sullivan continued. "Israel has accepted the proposal. The world has endorsed the proposal. Now it's time for Hamas to say yes to it."

Sullivan argued the latest multi-phase proposal is key to ending the war, returning hostages, and increasing the flow of aid into Gaza, while ensuring Israel's security and a better future for Palestinians.

"That's what's on offer," Sullivan said. "That's what Hamas needs to step up and take and we're awaiting to get their official response."

Asked whether Biden thinks Israeli Prime Minister Benjamin Netanyahu was prolonging the war for political gain — which he suggested in a Time magazine interview out Tuesday — Sullivan pointed to Biden's answer to a question Tuesday evening asking if Netanyahu was playing politics.

"I don't think so. He's trying to work out the serious problem he has," Biden said Tuesday.

"And from our perspective, we're not going to delve into Israeli politics," Sullivan added. "What we're going to do is focus on the fundamental task at hand, which is President Biden's effort to end this war, get the hostages home, make sure Israel's safe and make sure the Palestinian people have a decent future."

-ABC News' Fritz Farrow

An Israeli government official said the Israeli Prime Minister’s Office wasn’t informed that President Joe Biden’s Friday remarks would include a permanent end to the fighting.

“If you listen to what Biden said, you come to the impression that we agree to a permanent cease-fire without, or, without our conditions being met, and that's not the case,” the official said.

The official said the Israeli Prime Minister’s Office, including Prime Minister Benjamin Netanyahu, was informed 30 minutes before that Biden was giving a speech. The official said Netanyahu was told that the speech would focus on the hostages, with no mention of implementing a permanent cease-fire.

A senior U.S. official said the Biden administration "engaged with the Israelis at multiple levels before the president delivered the speech." The official said the U.S. specifically engaged with the Israeli Prime Minister's Office and the Israeli war cabinet.

The official also pointed to when Biden said in his speech that it was a proposal that the Israelis agreed to. The official noted that Netanyahu himself said that it was an Israeli proposal.

An Israeli official and two other Israeli sources who are familiar with the matter told ABC News that what Biden presented is indeed the outline of the Israeli proposal. The sources said the proposal was approved by all war cabinet members, including Netanyahu, and sent to the mediators earlier in the week.

The sources added that there are “interpretation gaps,” referring to the way the outline was presented by Biden.

Biden presented on Friday what he said was an Israeli proposal to draw the war in Gaza to a close.

Biden said the deal had been transmitted to Israel and Hamas, through Qatar.

The president said the first phase would last for six weeks and include a "full and complete cease-fire, a withdrawal of Israeli forces from all populated areas of Gaza [and] release of a number of hostages." Palestinians would also be able to return to their homes and 600 trucks of humanitarian aid would be delivered to Gaza every day.

The second phase would include a release of all remaining living hostages and the temporary cease-fire would become a permanent cease-fire with Israel withdrawing all forces from Gaza "as long as Hamas lives up to its commitments," Biden said.

In phase three, there would be a major reconstruction of Gaza.

-ABC News’ Britt Clennett, Dana Savir and Michelle Stoddart