The announcement come through Trip Advisor which is mentioned that the entire region will close to foreign tourist from 25th February and will reopen at 30th March.
This notice is no surprise because Tibet has been closed for foreign visitors except China from February to early April since 2008 because of the this period is marked with uprising. Besides, in March, Tibet commemorate Uprising Day at 10th March.
Plus Chinese authorites also fear from possible unrest at 30th March the date that Dalai Lama crossed into India and began his exile in 1959.
Alistair Currie of the Free Tibet campaign group says the Tibet Post:
“It’s very interesting that even though there is far less protest in the TAR at the moment and China has become increasingly willing to take diplomats and foreign media there over the last two years, they’re still not confident enough about the security situation to have foreigners there.”
This process is operated from the Tibet Tourism Bureau but there is no official reopening date signified yet.
While Tibet is open for travelers in other months, the region is under strict control from Chinese authorities and they cannot allow the independent exploration. So you need to join a tour helded from travel agency.