China announced a crackdown on the use of social media websites on Saturday following recent rumours that a coup was underway.

The decision comes after several web users posted pictures of Chinese military vehicles which they claimed were on the streets of Beijing.

Authorities closed 16 microblogging sites and arrested six people in connection with the rumours.

Two of the country’s most popular social media portals said they would stop letting users post comments for the next few days in an attempt to appease authorities.

Analysts said Chinese leaders were particularly sensitive to rumours of instability as the country prepares for a key leadership transition later in the year. The whispers spread shortly after the controversial sacking of Bo Xilai, a popular regional leader who many said was destined for the top.

China blocks many websites under a vast censorship system known as the “Great Firewall” but the use of social media sites has made monitoring increasingly difficult.