Madrid (Reuters): Spain's government set the clock ticking on Monday on imposing direct rule over Catalonia, after the region's leader missed a deadline to clarify whether he had declared independence.

The wealthy region threatened to break away following a referendum in October 1 that Spain's Constitutional Court said was illegal.

That plunged the country into its worst political crisis since an attempted military coup in 1981.

Catalan leader Carles Puigdemont made a symbolic declaration of independence last Tuesday, but suspended it seconds later and called for negotiations with Madrid on the region's future.

Madrid had given Puigdemont until Monday to clarify his position on independence with a "Yes" or "No", and until Thursday to change his mind if he insisted on a split - saying Madrid would suspend Catalonia's autonomy if he chose secession.

Justice minister Rafael Catala said on Monday the answer that Puigdemont had given in a letter to Spanish Prime Minister Mariano Rajoy was not valid.

"The question was clear but the answer is not," Catala told journalists.

While the government had not yet taken a decision and was still analysing the letter, it would take steps once the Thursday deadline has expired.