Catalan independence parties are seen as losing their parliamentary majority in an election, according to a poll published Sunday, though the wafer-thin margin between the two sides predicts a hard-fought campaign to December's ballot.

The poll was taken from last Monday to Thursday, just as Spain's central government was preparing to take control of the restive region, which then made a unilateral declaration of independence Friday.

The secessionist coalition formed by the ERC, PDeCAT and CUP parties would win 42.5 percent of the votes and 61-65 seats, the Sigma Dos survey for the conservative Spanish El Mundo newspaper said.

The majority in the Catalan assembly is 68 seats. In the last elections in 2015, separatists won 47.7 percent of the vote and conquered 72 seats.

The survey was published on the day a large anti-independence march was due to take place in the Catalan capital of Barcelona, backed by pro-union parties.

On Friday, Spanish Prime Minister Mariano Rajoy ordered the end of home rule for Catalonia and called a new regional ballot in response to the regional parliament declaring independence from Madrid.

Ousted Catalan leader Carles Puigdemont is calling for "democratic opposition" to Madrid's administrative takeover of Catalonia, but he has been told he risks arrest for "rebellion."