US Secretary of State Hillary Clinton has released the following statement:
I join President Obama in offering our sincere condolences for the loss of life and damage caused by the earthquake and tsunamis in Japan. We are closely monitoring the tsunamis that may impact other parts the world, including Hawaii and the West Coast of the United States.
"The U.S. Government has offered immediate disaster relief assistance, and we are working closely with the Government of Japan to provide additional help. Our consular officers in Japan and in the United States are working to gather information and assist U.S. citizens in Japan who may have been affected by the earthquake.
"The United States is an unwavering friend and ally of Japan, and we are committed to helping Japan respond and recover. Our thoughts and prayers are with the people of Japan during this difficult time."
Tony McNicol, a journalist in Tokyo, tells Al Jazeera that even that far from the epicentre, it was clear to people that the earthquake was a major one. He says people in Japan "are used to earthquakes" and did not panic, at least in Tokyo.
Christine Conner, an American living in Tokyo since 2009 with her husband, Clint, an attorney, and their three children, told Al Jazeera's D. Parvaz she realised how bad things were when her Japanese friends "looked ashen or in tears".
"They are usually stoic and the Westerners are the hysterical ones!"
She said that that the earthquake struck shortly after she picked up two of her daughters, aged four and six, from school.
"They were happily frolicking with four of their friends when one of the other mums looked over and said, 'It's an earthquake.' I couldn't yet feel it, and looked at her suspiciously. She followed this up with, 'It's the Big One.'" said Conner.
"That's when I started feeling seasick. I gathered the girls to me, mother-hen-like, yelling for them to sit. Other children and mothers started running in our direction, some in outright panic."
Being a California native, Conner did not panic initially, but, as she said, "It just didn't stop."
"[I] looked up and saw 40-story buildings swaying just in front of me and wondered what people thought in Haiti before their houses fell on top of them."
Conner also said there are "constant reminders" of the 1995 earthquake, which killed roughly 6,000 people.
"When you move into an apartment, the first thing you are shown is the evacuation maps and the emergency stash. There are several stories about 1995 - how bad the response was, how horrible the devastation was, and how much was learned," she said.
This time, though, she said that "authorities were out immediately. There were sirens sounding, with instructions that followed. I was near the girls' school, where they have standards in place for such an event. The teachers and principal came out to speak with us.
"Additionally, emergency personnel were roaming the neighbourhood."
Reports now that residents in coastal parts of northern California have evacuated their homes ahead of an expected tsunami.
Authorities have warned that waves could reach two metres when the tsunami reaches the shores.
Large waves triggered by the Japanese earthquake have hit Taiwan, Indonesia and Hawaii, but there have been no reports of damage so far.
Osman Demirtas, a 29-year-old Turkish man living in Yokohama, just west of Tokyo, has told Al Jazeera's D. Parvaz he walked the 22km journey home from his office in the capital after transport was halted following the quake.
"As precaution for another quakes, all transportation is stopped in Tokyo metropolitan area. Some people are walking and some will stay over workplace," Demirtas, a financial controller, said.
"There were thousands walking home at the beginning and now I am in Yokohama city, there are only tens of people. People are quite calm, enjoying walking. And some drinking beer."
More video amateur video from Japan, taken by panic-stricken residents during the earthquake: