Officials say that there isn't a specific threat, but thousands of officers have been staffed to prevent any potential attacks.
At Union Station, sheriff's deputies with bomb sniffing dogs were scouring subway platforms and train cars. Passengers were also subjected to random baggage checks.
LAPD Chief Charlie Beck says security has also been beefed up at LAX. There is also extra enforcement this weekend keeping an eye on buildings and areas of the city that could be potential targets.
"While we have nothing that points to Los Angeles, we all have to be constantly aware," said Beck. "So I ask people see something, say something."
Police say the public has a role to play in preventing terrorism, which is why they are asking everyone to stay alert.
Meanwhile, Los Angeles paid tribute to those who lost their lives during the terror attacks on Friday.
There was a somber ceremony commemorating the 10th anniversary of the Sept. 11 attacks in the front steps of L.A. City Hall.
"The enduring legacy of that day is remarkable heroism and generosity of American people," said Bradley Burlingame. His brother was the pilot aboard American Airlines flight 77, the Los Angeles-based plane that crashed into the Pentagon.
Mayor Antonio Villaraigosa and Beck were among several dignitaries who spoke at the commemoration ceremony. As many as 200 people gathered to hear the emotional speeches.