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

President Joe Biden outlined Israel’s cease-fire proposal accurately in his Friday speech, the White House maintained Monday, pushing back on suggestions he miscommunicated the offer.

"The Israeli foreign minister himself acknowledged that this was the Israeli proposal ... and we're confident that it accurately reflects that proposal, a proposal that we worked with the Israelis on," White House national security communications adviser John Kirby told reporters.

Kirby also argued that Biden "felt it was important" to reveal details from ongoing cease-fire negotiations for the first time, saying it was meant to apply pressure on Hamas, not to corner Israeli Prime Minister Benjamin Netanyahu.

"We don't typically go through the details of these kinds of proposals," Kirby said. "But in this case, given where we are, given how much longer the hostages have now been held, given the fact that Hamas has reneged on several past occasions, on proposals that were sent to them, and given the fact that the Israelis really did work hard to come up with this proposal, and did so in good faith, the president felt it was important for the first time to publicly lay that out."

"This wasn't about jamming the prime minister or the war cabinet," Kirby added. "This was about laying bare for the public to see how well and how faithfully and how assertively the Israelis came up with a new proposal, how it shows how much they really want to get this done."

Kirby said Biden delivered the speech on Friday afternoon because the deal was presented to Hamas the night before.

"We're awaiting an official response by them now to take the deal," Kirby said. "This gives them what they've been looking for, which is a cease-fire and over time, and through the phases, the potential withdrawal of Israeli forces from Gaza."

-ABC News’ Fritz Farrow