At least 200 people gathered at Scotland’s Faslane naval base on Monday to protest the installation of the U.K.’s Trident nuclear weapons deterrent system. The protesters blocked all entrances to the facility.

Trident is a sea-based system, encompassing submarines, missiles and warheads, and it has been backed by both major parties in the U.K. ahead of the general elections, despite growing opposition from voters and lawmakers. “Trident is an obscenity,” Scottish Green Party member and Glasgow lawmaker Patrick Harvie said, according to local news site STV. “Through direct action and through the ballot box we can make the case for the UK to play a new role on the world stage.” 

Members of Scrap Trident gathered to call for the closure of the Faslane base. They had previously spoken with local police officials in early April to ask that they refrain from making arrests at what they promised would be a “peaceful and lawful” protest. A spokesperson for the Ministry of Defense said they recognized the protest as legitimate, but added that the “safety and security of the site will be maintained at all times,” the National reported.

However, on Monday, social media posts from the protests appeared to show police making some arrests. 

An open letter, published in the Guardian, calls for the U.K. to abandon Trident and become the first permanent member of the U.N. Security Council to give up its nuclear weapons in the process.

“Instead of protecting us, hosting nuclear weapons makes us a target for the disaffected. And any accident would lead to a humanitarian disaster. Having nuclear weapons diverts resources and attention from tackling our most urgent security problems, including climate and environmental destruction,” the letter, whose signatories include the band Massive Attack and linguist Noam Chomsky, read.

Meanwhile, Defense Secretary Michael Fallon accused Labour leader Edward Miliband of being "willing to stab the UK in the back," alleging that Miliband would seek to scrap Trident in order to curry favor with the Scottish National Party (SNP). However, Miliband dismissed the attack as “embarrassing” to Fallon, and reaffirmed his commitment to the Trident program.

Polls suggest that if the U.K.’s ongoing general election ends in a hung parliament, the SNP could emerge as the third-largest party, making it valuable to either of the major parties as a potential coalition partner. SNP leader Nicola Sturgeon has made it clear that any support from the SNP would require a commitment to ending Trident.