Splits have emerged among Catalan separatist leaders over their plans to unilaterally declare independence following a secession referendum deemed illegal by Madrid.

Catalonia's leader Carles Puigdemont has threatened to declare independence "within days", but the region's business minister Santi Vila proposed a "ceasefire" in the row with Spain's central government.

In an opinion article published in Catalan daily Ara he urged the pro-secession camp to "reflect on the usefulness and consequences" of a declaration of independence.

Puigdemont put off until Tuesday an appearance in the regional Catalan parliament at which time some leaders have called for the declaration to be made.

The session of parliament to analyse the results of last Sunday's referendum was initially scheduled for Monday but Spain's Constitutional Court ordered that it be suspended.

The Catalan government has also not yet officially ratified the results of the vote, a move which would open a two-day period in which the parliament can declare independence.

Participants in the referendum opted overwhelmingly for secession, but turnout was only 43 percent as Catalans who favour remaining part of Spain mainly boycotted the ballot.

While Vila urged caution, Puigdemont is under strong pressure from the far-left CUP party -- whose support his government needs to pass legislation -- to move quickly.

"The inescapable, inevitable moment of exercising self-determination has arrived," said CUP lawmaker Carles Riera.

- 'Real alarm' -

Puigdemont's predecessor Artur Mas also weighed in, telling Britain's Financial Times that Catalan leaders should focus not on "how to proclaim independence, but instead on how to make it effective."

Analysts said the Catalan government risks losing international sympathy and giving Madrid an excuse for a hardline response if it makes a declaration of independence based on an unconstitutional vote.

But if it waits too long to act on the results of the plebiscite it could see the momentum behind the independence movement fizzle.

The debate is not just limited to politicians -- supporters of the separatist cause are also divided over what strategy to follow.

"I have an inner conflict. I do not want a unilateral declaration of independence to happen that will last five minutes," said Olga Jubany, an anthropology professor in Barcelona. 

"The strategy (of independence) was never 'we are going to impose it'. It is not the strategy I would like to follow."

Joan Botella, dean of political science at the Autonomous University of Barcelona, said "there is a sense of real alarm, not just uneasiness" in Catalan society.

Spanish Prime Minister Mariano Rajoy, who is under pressure to show a harder line towards the separatists, has urged Puigdemont not to go ahead with the independence declaration to avoid "bigger problems".

His comment was seen as a reference to a never before used article of the Spanish constitution which allows the central government to suspend the authority of a regional government.

"There are few hours left to avoid a head-on collision... these are critical hours," said Botella.

- Urging no immediate decisions -

Since the referendum Puigdemont has called for international mediation.

Switzerland has been in contact with both sides in the dispute "but the conditions for facilitation do no exist at the moment," the country's foreign ministry said.

Without foreign mediation, the other option is for mediation within Spain.

Puigdemont has met with a commission set up by Barcelona's law society made up of academics and representatives of unions and the business world.

It has recommended that both sides not take any "immediate decisions," the withdrawal of the thousands of extra police sent to Catalonia ahead of the referendum, and for a "dialogue commission" to be set up.

"These are crucial hours, we cannot expect a mediator to suddenly emerge or that both governments accept a proposal for dialogue," said Xavier Arbos, a professor of constitutional law at the University of Barcelona