Fears of terrorism and stepped-up security provide a sobering backdrop to planned New Year's Eve celebrations around the world.

In the United States, federal and local security officials are tightening security in high-profile locations, including New York's Times Square and the Rose Bowl festivities near Los Angeles. In Belgium and Turkey, police said they disrupted terrorist plots that would have targeted celebrations to ring in the New Year in the capitals of those countries.

Here's a look at the latest news on that front around the world:

UNITED STATES

Before President Barack Obama left for his Hawaii vacation, his top security officials briefed him about a threat, originating from overseas, of possible attacks in New York, Los Angeles and Washington between the Christmas and New Year's holidays, according to senior U.S. officials briefed on the matter

The officials said the threat was uncorroborated and was based on a single source, and it didn't mention specific locations in the cities. But they said they are always concerned about "soft targets" such as large gatherings and mass transit systems.

In the wake of attacks in Paris San Bernardino, California , and elsewhere, the FBI is boosting the number of agents and staff in some of its 24-hour command centers around the country, including in New York, Washington and Los Angeles.

About 6,000 police officers will fan out around Times Square for the annual New Year's Eve celebration there, Police Commissioner Bill Bratton said.

"We are not aware of any threat at this time that we deem credible," he said.

Among the tools the police will use to guard against would-be criminals or terrorists: cops on helicopters and boats along with hundreds of additional mobile cameras and radiation detectors. It's a grim reminder of the threats posed by terrorist organizations from around the world. In addition, hundreds of officers will carry rifles, said James O'Neill, a top police official in New York.

"We are ready," New York Mayor Bill de Blasio said this week. He called New York "the best prepared city in the country to prevent terrorism and to deal with any event should it occur."

New York Police Commissioner Bill Bratton, left, and Mayor Bill de Blasio say the city is ready. They're shown in a photo from a few weeks ago.

There will be more cameras watching the route of the Rose Bowl Parade, Pasadena Police Chief Phillip Sanchez told reporters.

"It's not the first year we've had cameras, but there will be more of them installed by (the Department of Homeland Security)," Sanchez said.

The additional cameras are part of more resources and money being used for the event and the Rose Bowl game, which are considered elevated security events for the first time.

The chief of the Los Angeles Sheriff's Department said more officers will be at the parade and later at a celebration at Grand Park.

"This is probably largest deployment they've ever had," he said.

BELGIUM

There will be no New Year's festivities in Brussels, not even fireworks, the capital city's mayor told CNN affiliate RTL.

Mayor Yvan Mayeur cited the nation's heightened terror alert.

Belgian authorities have arrested two people on suspicion of being involved in a plot to attack "emblematic sites" in Belgium's capital during New Year's celebrations, the country's federal prosecutor's office said Tuesday.

The men are members of a Muslim biker gang called the Kamikaze Riders and are suspected to have discussed attacking Brussels' Grand Place square and other places where crowds gather, as well as police and military facilities, a senior Belgian counterterrorism official told CNN on condition of anonymity.

Belgian soldiers patrol Tuesday at the Grand Place in Brussels, mentioned as a possible terror target.

The plot appears to have been inspired, but not directed, by ISIS, the counterterrorism official said.

TURKEY

Turkish police say they've arrested two people with alleged ISIS ties on suspicion of planning a bombing attack in Turkey's capital on New Year's Eve.

The two were arrested Wednesday as they allegedly scouted potential attack locations in the capital, Ankara, the Ankara governorship said.

The pair had a vest with explosives and a backpack "ready for use" -- with iron marbles and sticks and other materials for use in bomb-making -- the governorship said.

Investigators believe the pair intended to target two locations near Ankara's Kizilay district, the country's semiofficial Anadolu news agency reported, citing the Ankara chief prosecutor's office.

On October 10, two bombings outside Ankara's main train station killed more than 100 people. No group claimed responsibility for that attack, though Turkish officials have blamed ISIS, which captured vast swaths of neighboring Syria and Iraq.

AUSTRIA

There is heightened security in Vienna after police there said several European cities were warned of possible terror attacks. The warning did include the names of several possible attackers Vienna police investigated without finding "concrete further results," authorities in the Austrian capital said Saturday.

Police will initiate more thorough security checks, ensure quick readiness in case of an emergency and increase vigilance in terms of empty suitcases and bags for New Year's, Vienna police said

One of the big events on New Year's Eve is the Hofburg Silver Ball. There are also big outdoor events on Graben Street and in front of city hall.

BANGLADESH

The U.S. Embassy in Bangladesh warned U.S. citizens this week that attacks against hotels and clubs are possible in the capital, Dhaka, in the next few days, perhaps in connection with New Year's Eve celebrations.

The U.S. Embassy in Bangladesh warned of possible attacks in the capital, Dhaka.

The embassy did not say what led to the warning.

The warning came a month after the U.S. State Department issued a travel alert for Americans traveling to the South Asian country, citing what it described as a potential for extremist violence in light of recent attacks claimed by ISIS.

In its warning Tuesday, the embassy said Dhaka police have increased security measures for New Year's Eve, including a ban on outdoor parties after 8 p.m.

CHINA

The Shanghai government said there will be no organized New Year celebrations on the Bund, a popular riverfront area, China's state-broadcaster CCTV reported.

Shanghai spokesman Xu Wei warned people who go to the Bund of their own on New Year's Eve will have to comply with public order rules.

The announcement follows last year's NYE stampede in Shanghai that killed 36 people and injured 49 more.