Chinese authorities have tightened security in Beijing ahead of the Communist Party's National Congress, which begins on Sunday.

Many police officers and other personnel have been deployed around the Great Hall of the People, the venue for the congress.

Images circulating online show banners calling for reform, with smoke rising in the background.

Beijing authorities have imposed controls on the sale of gasoline and handling of hazardous materials until the end of the party congress to prevent them from being used for arson and explosions.

Around 2,300 representatives are expected to take part in the congress, which takes place every five years.

They will decide on a new leadership lineup as well as basic political and economic policies.

The delegates are expected to incorporate into the party constitution a slogan expressing loyalty toward President Xi Jinping.

The 69-year-old Xi is widely expected to secure an unprecedented third term, defying a custom of party leaders retiring at the age of 68.