Mahmoud Ahmadinejad has been sworn in for a second term as Iran's president, after weeks of post-election unrest.
In an address after the ceremony, he criticised foreign powers who have cast doubt on the validity of the election, saying Iran would resist them, the BBC reports.
Opposition supporters protesting outside parliament were met by hundreds of riot police.
Germany, France, Britain and the United States all said they would not be sending letters of congratulation to Mr Ahmadinejad.
At least 30 people died during the street protests which followed the 12 June poll.
Mr Ahmadinejad now has two weeks to form a government that must then be approved by parliament.
Taking his oath of office, broadcast live on state television, Mr Ahmadinejad promised to "protect the official faith, the system of the Islamic revolution and the constitution".
He vowed to "refrain from being autocratic and to protect the freedom and dignity of individuals".
Following the swearing-in, he used his first address to defend the official results of the election - which gave him an overwhelming victory - and criticised Western powers' response to the disputed poll.