Barack Obama has been sworn in as the 44th president of the United States.

The ceremony marks the start of a four-year term in office for Barack Obama as president and his running mate Joseph Biden as vice-president.

President Obama was sworn into office on the steps of the US Capitol at noon on January 20th.

In his inaugural address, President Obama said: "Today I say to you that the challenges we face are real. They are serious and they are many. They will not be met easily or in a short span of time. But know this, America - they will be met."

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