There have been at least three explosions in two different locations in the Belgian capital city of Brussels Tuesday morning.
Belgian media is reporting at least 13 people have died and Prime Minister Charles Michel said that "there have been many injured."
Two explosions occurred in the departure hall of the city's international airport and another happened on the tracks of one of the city's subway stations.
The entire subway system has been closed and the Zaventem airport is being evacuated.
These blasts come days after the capture of Salah Abdeslam, the main suspect in the Paris attacks in November who remained at large for four months before his arrest.
In the wake of his arrest last week, the Belgian Interior Minister warned that officials were worried that Abdeslam's capture may prompt further attacks.
There has been no official designation as today's attacks as the act of terrorists, but the
All public transport in Brussels is now closed.
The European Union, which has its de facto capital in Brussels, has urged all employees to either stay in their offices or at their homes.
All EU institutions have been placed on alert level orange and all meetings inside any of their buildings have been cancelled.
The U.S. embassy in Brussels has urged American citizens to shelter in place and avoid all public transport.
The explosions have prompted an international response, with senior law enforcement officials in the U.S. confirming to ABC News that Homeland Security and FBI officials are monitoring closely.
U.S. Attorney General Loretta Lynch has been notified.
The New York Police Department has also confirmed that they are monitoring the situation closely.
The NYPD is not the only police force amping up security in the wake of the attacks.
The French Interior Minister confirmed that 1,600 extra police officers have been deployed near French transportation hubs in the wake of today's explosions.
France had already sent out an extra 500 extra police near the country's borders after Abdeslam was arrested last week.
The Metropolitan Police in London have released a statement confirming an increase in deployment.
Assistant Commissioner Mark Rowley, the national lead for Counter Terrorism Policing, released a statement saying that "forces across the UK have increased policing presence at key locations, including transport hubs, to protect the public and provide reassurance. This is not in relation to any specific information or intelligence."
The attacks have been classified as terror attacks by the Belgian federal prosecutor.
He said that at least one of the explosions was the work of a suicide bomber.
Belgian Prime Minister Charles Michel just addressed the public in French.
"What we were fearing has happened," he said.
"They have striked us in a cowardly way."
From ABC News' David Kerley in Washington:
A senior government official confirms that TSA administrator Peter Neffenger is in Brussels and was apparently on airport grounds around the time of the bombing.
Neffenger is on a trip to meet with European counterparts and landed in Brussels in the morning. It is unclear exactly when his flight landed or if he ever made it to terminal.
He is in a safe place in Brussels at this hour.
From ABC News' Josh Margolin in New York:
The Port Authority police department in New York is stepping up security at its three major airports -- JFK, LGA and Newark -- with heavy weapons and also is employing high visibility anti terrorist patrols at PATH train system and the World Trade Center.
From ABC News' Jack Date in Washington:
A federal law enforcement source tells ABC News we can expect to see an increased law enforcement presence on transit and rail systems in major cities throughout the country.
The official Twitter account for the city of Paris has changed its avatar to the Belgian flag and posted a tweet saying they are standing with the Belgian people and are thinking of them.
The Secretary General of NATO announced that they will be increasing the alert state at their headquarters in Brussels.
"I am deeply saddened by the attacks here in Brussels this morning. The heavy human toll is tragic," Jens Stoltenberg said in a statement.
"This is a cowardly attack. An attack on our values and on our open societies. Terrorism will not defeat democracy and take away our freedoms."
As a result of the explosions at Zaventem airport, 44 flights were diverted, according to FlightRadar24.
Four other flights are in the air right now.
There have been 214 flights that were scheduled to arrive in Brussels that have since been cancelled.
The French Army posted a message of support for Belgium on Twitter, along with a photo of soldiers with heavy weapons at what appears to be a transportation hub.
“More than ever, the French army is mobilised against the terrorist threat. We will win this war,” Gen. de Villiers said in a quote posted on the army's Twitter account.
From ABC News' Louise Dewast in London:
A university in Brussels has been evacuated as a precaution.
There are 24,000 students who study at Universite Libre de Bruxelles.
All the campuses have been evacuated as a precaution, a spokeswoman confirms to ABC News.
Belgian Ambassador to the U.S. Johan Verbeke told reporters that at the airport "statements... cries" had been pronounced in Arabic, "so that is the first indication of what the source is maybe, but I don't want to elaborate on that because that is definitely something that has to be further investigated."
Verbeke said he did not know what was said in Arabic.
From ABC News' Justin Fishel in Washington:
State Department spokesperson John Kirby issued a statement this morning, noting that Secretary John Kerry has been informed about the attacks.
"[Kerry] He is closely monitoring the situation and extends his condolences to all those who have fallen victim today," Kirby's statement said.
From ABC News' Ben Siegel in Washington:
Rep. Adam Schiff, D-California, is the ranking Democray on the House Intelligence Committee and said that he has received a preliminary briefing on the attacks.
Schiff said in a statement that the attacks "bear all the hallmarks" of an "ISIS-inspired" or "ISIS-coordinated" plot.
Former Secretary of State Hillary Clinton spoke on "Good Morning America" today, saying how she believes "we need to intensify and broaden our strategy" in terms of security threats in Europe.
"This is a horrific attack right in the heart of Europe," she said.
She called for "a real upping of our security cooperation."
"There has to be some honest reckoning about what works and what doesn't work," she said.
"There are still a lot of outdated laws and practices in law enforcement -- particularly in Europe -- that have to be updated and changed."
From ABC News' Dada Jovanovic:
A spokesperson for the public transportation department in Brussels confirmed new details about the explosion that occurred in the subway station.
The explosion happened at 9:11 a.m. local time and happened just as the train was leaving the station, heading towards the center of the city.
The explosive device went off in the second of the train's five cars as it was still on the platform.
All passengers were evacuated immediately.