LONDON — A court in Bahrain sentenced a prominent democracy advocate on Wednesday to five years in prison for tweets about abuses in prisons and the Saudi-led war in Yemen, continuing the crackdown that crushed the Arab Spring uprising there seven years ago.

The sentencing of the advocate, Nabeel Rajab, is the latest step in a long crackdown on dissent in Bahrain, a tiny island kingdom that is home to the United States Navy’s Fifth Fleet. Backed by rulers in neighboring Saudi Arabia and the United Arab Emirates, Bahrain’s Sunni Muslim royal family has used tanks, riot police officers, sweeping arrests and tight censorship to thwart demands for democracy among the Shiite Muslim majority, and the resulting conflict has inflamed sectarian tensions around the region. The repression has presented Washington with one of the most awkward conflicts between its professions of support for human rights and its military commitments in the Persian Gulf.

Mr. Rajab, 53, president of the Bahrain Center for Human Rights, is a leader of the pro-democracy movement that came to life in 2011, during the Arab Spring uprisings across the region. He was sentenced to three years in jail the next year, on charges of inciting protests against the government, and he has spent much of the intervening time in and out of prison on a series of charges related to his criticism of the monarchy. He is already serving a two-year sentence handed down in July for comments he made in television interviews, and faces more charges related to an Op-Ed published in The New York Times in 2016, “Letter From a Bahraini Jail.”

In it, Mr. Rajab recounted a recent meeting with John Kerry, then the secretary of state “I would like to ask Mr. Kerry now: Is this the kind of ally America wants?” he wrote. “The kind that punishes its people for thinking, that prevents its citizens from exercising their basic rights?”