The swearing-in ceremony at Spain's parliament got off to a rocky start Tuesday when several Catalan separatist politicians changed the wording of their oaths to declare loyalty to the result of an illegal independence referendum held in the region back in October 2017.

Lawmakers were taking their seats for the first time since snap elections on Apr. 28, which were called for and won by acting prime minister Pedro Sánchez's Socialist Party (PSOE).

"I promise, because the law requires it of me, to be loyal to the democratic mandate of Oct. 1 and the Catalan people," several members of the Republican Left of Catalonia (ERC) said when swearing on the Constitution, using a set of words traditionally associated with separatist causes.

"For the freedom of political prisoners and exiles, for the Catalan republic, yes, I promise," Gabriel Rufián, who is likely to be ERC spokesman in parliament, said.

Albert Rivera, leader of the center-right Ciudadanos, protested and asked the new parliamentary speaker, Meritxell Batet – a member of PSOE's Catalan branch – to issue a call to order. Several other members of Spain's mainstream and unionist parties, mostly on the right, banged their fists on their desks.

Batet said she would not halt proceedings and defended a diversity of politics in Spain's lower chamber.

"We are all of the people, but none of us are the people," she said.

In what was a novelty in the chamber, five Catalan politicians currently facing charges linked to separatism in a high-profile, Supreme Court trial, briefly left preventative prison in order swear in as members of Spain's parliament and senate following recent snap elections.

They were ERC leader Oriol Junqueras and Junts per Catalunya (Together for Catalonia, JxCat) MPs Jordi Sánchez, Josep Rull and Jordi Turull.

JxCat, the party of self-exiled former Catalan regional president Carles Puigdemont, also welcomed a new senator, Raül Romeva, who caused a stir when swearing in by saying he would abide by the Constitution "as a political prisoner."

All are among the 12 Catalan separatists leaders currently on trial for charges ranging from rebellion and sedition to misuse of public funds related to their alleged activities promoting and facilitating an illegal independence referendum in Catalonia and unilaterally declaring independence back in October 2017.

Spanish media attention paid close attention to who greeted who in the chamber.

Police escorted them out of the chamber once the session concluded.

Although PSOE came out of the general elections with most votes, no party secured enough seats to form an absolute majority in the lower chamber. The right-wing, traditionally dominated by the Popular Party, fractured into three.

Meanwhile in the Senate, Spain’s upper chamber, the Socialist Party has an absolute majority for the first time in 30 years, with 140 seats out of a total of 266.

Another novelty in the lower chamber, known as the Congress of Deputies (lawmakers) in Spanish, came in the form of the far-right party, Vox, led by Santiago Abascal.

Vox's 24 MPs, members of the first far-right party to enter Spain's parliament since the transition into democracy after late military dictator Gen. Francisco Franco in 1975, arrived at parliament early and decided to sit in the left-hand portion of the hemicycle, an area usually reserved for the PSOE.EFE-EPA