Spain's central government says it will send in national police to ensure security in Catalonia if regional authorities fail to stop recent disruptions to major highways by pro-independence protesters.
The warnings follow the blocking of a highway across Catalonia for more than 15 hours on Saturday. Separatist groups on Sunday allowed cars to pass through without paying the mandatory toll.
Three cabinet members of the national government sent letters late on Tuesday urging their Catalan counterparts to explain why the Mossos d'Esquadra police, which is controlled by the regional government, didn't intervene.
After last year's independence attempt in the northeastern region led to an unprecedented political crisis, Catalan and central authorities began a timid dialogue in June when a new center-left administration took power in Madrid.