The door to the Palestinian-American Community Centre in Clifton, New Jersey, was always open – but now it is locked and people are allowed in only after they have identified themselves.
This is part of bolstered safety measures being seen in Arab-American communities across the US as the Israel-Gaza war escalates.
Rania Mustafa, PACC's executive director, said the centre has so far received 10 threatening phone calls, including two on Friday, as well as harassing emails and messages on social media.
“We're scared and we're afraid for our people in Gaza and in the West Bank, and we are also scared for our community here,” Ms Mustafa told The National.
“We're seeing instances of people being silenced or being verbally attacked, and it is not OK.”
Major cities in the US, including Washington, New York, Los Angeles and Chicago, said they were on high alert and would step up police patrols, especially around synagogues, mosques and other areas frequented by Muslims and Jews.
But authorities have insisted they are unaware of any specific or credible threats.
The heightened concerns come after Hamas gunmen from Gaza launched an attack on parts of southern Israel on Saturday, killing more than 1,300 people and taking scores hostage.
Israel retaliated by launching an attack on Gaza, which is home to 2.3 million Palestinians. About 1,800 have been killed so far, and the conflict is expected to escalate further.
Israel has urged the more than one million Palestinians living in the northern Gaza Strip to leave the area ahead of a possible ground invasion.
The White House said President Joe Biden has directed law enforcement to enhance security in the US, especially in Jewish and Muslim communities.
“At this time, none of our intelligence agencies have any specific intelligence indicating a threat to the United States stemming from the Hamas terrorist attack in Israel,” White House National Security spokesman John Kirby told journalists on Friday.
“That said, we continue to remain vigilant to any and all possible threats federal, state and local law enforcement are working around the clock to provide an authority to prevent any violence from occurring.”
Arab groups say police alerts embolden people who are already radicalised and endanger Arab and Muslim Americans.
“For us, that's a clear dog whistle,” Muhammad Sankari, organiser at the Arab American Action Network, a non-profit in Chicago, told The National, following the release of an FBI statement on heightened security in the city.
“This is the largest Palestinian-American community in the United States – what they are saying is that US law enforcement sees this community as a threat.”
The American-Arab Anti-Discrimination Committee said it has received 40 calls from Arab and Muslim Americans about harassment or attacks over the past two days.
In a typical month, 50 to 60 such calls are recorded.
Abed Ayoub, national executive director of the ADC, told The National that the reports also include FBI officers visiting a mosque in Texas and the detention of two Palestinian Americans by Immigration and Customs Enforcement agents.
“Hate rhetoric online and in schools and just in general the atmosphere is very tense,” he said.
“It's very reminiscent of what happened post 9/11.”
US media reported that the New York Police Department hate crimes unit was investigating at least two crimes against Palestinians and Arabs this week.
On Wednesday, three assailants who were waving Israeli flags and shouting anti-Palestinian rhetoric allegedly assaulted three Arab Americans.
Earlier that day, a man holding a Palestinian flag was attacked in Williamsburg, police said.