SEATTLE — When a giant Royal Dutch Shell rig arrived last Thursday at the Port of Seattle, it was an unwelcome sight for a number of city officials and environmentalists. The 300-foot tall Polar Pioneer is one of two drilling rigs that Shell plans to use to explore for oil off the coast of Alaska this summer.

Earlier this month, the city declared that the port, where Shell has rented space to store its fleet, would need a new permit to house the rigs. The oil giant responded defiantly, hauling the mammoth platform into port without city approval. On late Monday, Seattle issued a notice of violation to the port, Shell and Foss Maritime, the company leasing the space to Shell.

The notice arrived amid several days of protests over the rig. Earlier on Monday, Seattle city councilor Kshama Sawant, a socialist and former Occupy activist, joined a few hundred demonstrators who blocked the gates of the terminal where the rig is moored. “The eyes of the world are on Seattle this week,” said Margo Polley, a city transportation worker who participated in the protest on her day off. “Hopefully we can build this movement, make it huge and stand up to these fossil fuel giants.”

The arrival of the rig followed the Obama Administration’s announcement last Monday that it had provisionally approved Shell’s plans to drill exploratory wells in the Chukchi Sea off Alaska’s northern coast. But the city of Seattle has other views. The same day, the city counci unanimously passed a resolution prodding the port to rethink Shell’s presence here. The resolution echoed sentiments expressed earlier this month in a public statement by Seattle Mayor Ed Murray, who exhorted the port to “make a bold statement about how oil companies contribute to climate change, oil spills and other environmental disasters.”

Washington State often calls itself “the other Washington.” But politics here lean both far left and deep green. The city has a reputation as a hotbed of activism. Most famously in 1999, tens of thousands of people took to the streets in an attempt to stop the negotiations of the World Trade Organization, and the mayor declared a state of emergency. These days, a number of prominent Seattle leaders are far less receptive to the fossil-fuel industry than they are to the throngs of environmentalists who showed up to protest — although Shell does have allies here, including the port commissioner Bill Bryant (who is also a gubenatorial candidate) and some labor groups, who say Foss is bringing jobs to the city.

On Saturday, hundreds of people made their way in kayaks, sailboats and other vessels across the waters of Seattle’s Elliott Bay to the feet of the rig, at the edge of a 100-yard “safety zone" enforced by police. The protest was evocative and colorful — roughly 1,000 people gathered on land and water, according to an organizer with Greenpeace, one of several groups organizing the demonstrations. The activists cheered, chanted, sang, then clustered together on the water and collectively raised a banner in front of the city skyline that read “Climate Justice Now.” A few city leaders joined by boat, including former Seattle mayor Mike McGinn (who called the rig "the deathstar" on Twitter), Sawant, and City Councilor Mike O'Brien.

Seattle officials admit there’s little they can do to alter Shell’s plans. “Besides making a statement and challenging their permit, the city has fairly limited authority when it comes to this oil rig," Mayor Murray told KING-5, an NBC affiliate.

But the protest organizers expressed optimism and stressed that the recent demonstrations were just a beginning. “I like to think that if enough people wanted it to happen and took action for it, we could actually keep this rig from going to the Arctic,” said Bill Moyer, an organizer of Saturday’s demonstration.

The activists say they will keep pressure on the corporation until it heads out of Seattle, likely in June. They are raising money through an Indiegogo campaign to rent a 4,000-square-foot barge that would float in Elliott Bay for at least a couple of weeks. Powered by solar panels, the barge, nicknamed the “People’s Platform” will broadcast anti-drilling messages from around the world on a video screen, according to Jen Williams, organizer with a local activist group called the Mosquito Fleet.

Since Shell’s failed attempt at a shallower exploratory Arctic well in 2012, environmental groups in Seattle and across the region have paid close attention to the petroleum company’s push to drill in the polar north. In April, a coalition of national organizations, including Greenpeace, placed a full-page ad in USA Today calling on President Obama to stop Arctic drilling. Cassady Sharp, Greenpeace spokesperson, said, “Shell should expect protests every step of the way. Arctic drilling has risen to the profile of Keystone XL,” the stalled tar-sands pipeline that became a national cause célèbre after environmentalists staged continuous protests against it. Seattle activists hope to keep it that way.