The vice minister of public security and head of Beijing's Public Security Bureau, Fu Zhenghua, urged officers to increase security in the city as he visited police stations and SWAT checkpoints along Beijing's main thoroughfare, Chang'an Avenue, on Saturday.
Police must be ready to "deal a deadly blow to enemies at the critical time", the official Xinhua news agency cited Fu as saying in a report on Sunday, Reuters reported.
Chinese police do not always carry firearms, but top leaders have warned that security threats are mounting.
Police in Beijing have already stepped up armed patrols after five people were killed and 40 hurt when a car plowed into a crowd and burst into flames near Tiananmen Square last October. The dead included three people in the car identified by authorities as militants from the western region of Xinjiang.
Xinjiang is the home of Muslim Uighurs who speak a Turkic language. China has blamed previous attacks on militants it says seek to establish an independent state there called East Turkestan.
Around 200 people have died in attacks blamed on Xinjiang militants in China in the last year or so, and the authorities have launched a campaign to stop the unrest, detaining hundreds and executing many others.