British officials have voiced concern over the escape of a terror suspect who vanished after switching into women's clothes at a west London mosque.

The Metropolitan Police say it's still trying to find Mohammed Ahmed Mohamed, 27, one of about nine people subject to a restrictive form of government surveillance when he disappeared on Friday.

Authorities say security camera footage showed the Somali-born suspect slipping away from the mosque in a niqab, an all-encompassing garment worn by conservative Muslim women.

Mohamed was being tracked under the government's Terrorism Prevention and Investigation Measures, a stringent form of surveillance imposed on people suspected of terror ties.

It's not exactly clear how he managed to escape the program's GPS tagging.

U.K. opposition politician Yvette Cooper called the incident "extremely serious."