NEW YORK- Victims' relatives, survivors and rescuers are observing the 16th anniversary of the Sept. 11 terror attacks at ground zero.

Monday's commemoration began with a moment of silence and tolling bells at 8:46 a.m. It's the time when a terrorist-piloted plane slammed into the World Trade Center's north tower.

Then victims' relatives began reading the names of the nearly 3,000 people killed when four hijacked planes hit the trade center, the Pentagon and a Pennsylvania field on Sept. 11, 2001.

Republican President Donald Trump, a native New Yorker, is observing a moment of silence at the White House and then participating in an observance at the Pentagon. It's his first time observing the anniversary as president.

There is also a ceremony at the Flight 93 National Memorial near Shanksville, Pennsylvania.