BEIJING — Most nights, a mixed crowd of young Chinese and foreigners, many of them students, cram the sidewalks along Caijing Dong Street, drinking alcohol and snacking on street food to the sound of thumping music as they course from one club to the next. Recently, though, there has been a more subdued vibe.

The international atmosphere along this strip, known as Wudaokou and located in the heart of Beijing’s university district, has fallen afoul of political sensibilities. At least two bars say they have been told by the local police not to let in more than 10 foreigners at a time until March 22, after the end of the annual session of the National People’s Congress, China’s rubber-stamp Parliament.

There are concerns that the ban could signal a coming crackdown. A broader campaign by officials in Beijing to “clean up” the city is already underway. So far, the effort has targeted the old alleyways called hutongs, as well as crowded, slum-like migrant neighborhoods, leading some to say it is fundamentally changing the face of the capital.

The latest warning has raised fears that Wudaokou, known for its bars and boisterous night life, is next. On a recent Saturday night, the street was far more hushed than usual. Many foreigners, who make up a large part of the clientele here, had evidently decided to go elsewhere.