公安局的警察经常巡逻街道。

Gōng'ānjú de jǐngchá jīngcháng xúnluó jiēdào.

Police officers from the public security bureau often patrol the streets.

每个城市都设有公安局。

Měi gè chéngshì dōu shè yǒu gōng'ānjú.

Every city has a public security bureau.

如果发现可疑情况，请及时报告公安局。

Rúguǒ fāxiàn kěyí qíngkuàng, qǐng jíshí bàogào gōng'ānjú.

If you notice any suspicious activity, please report it to the public security bureau promptly.