Havana ? Cuban state agents rounded up more dissidents Friday in a campaign to root out growing opposition on the communist island. A nongovernmental human rights group said 72 dissidents had been arrested.

The crackdown, which marked an end to several years of relative tolerance for Cuba’s critical voices, was initially spurred on by allegations of dissidents conspiring with U.S. diplomats.

The detainees included more than a dozen independent journalists, owners of lending libraries, leaders of opposition political parties and pro-democracy activists who gathered signatures for a reform effort known as the Varela Project.

The crackdown alarmed international rights and press advocates, including former President Jimmy Carter, who called on Cuban authorities to respect human rights and “refrain from detaining or harassing citizens who are expressing their views peacefully.”

Paris-based Reporters Without Borders accused the government of taking advantage of the world’s preoccupation with the U.S.-led war in Iraq to carry out the roundup.

“Human rights in Cuba can therefore be viewed as one of the first cases of collateral damage in the second Gulf war,” said Robert Menard, the group’s secretary general. “Human rights in other countries could also soon suffer the same fate.”

Friday the nongovernmental Cuban Commission on Human Rights and Reconciliation reported 72 dissidents had been detained.

“The only crime committed by these prisoners is the promotion of ideas that are forbidden in Cuba,” said Jose Miguel Vivanco, executive director of the Americas division of the nongovernmental Human Rights Watch.

The leadership of the Inter-American Press Assn., currently meeting in San Salvador, El Salvador, expressed concerns about the arrest of contributors to De Cuba, a new monthly magazine with articles by independent reporters.

The American Society of Newspaper Editors sent a letter to Cuban Foreign Minister Felipe Perez Roque urging the release of those detained.

Meanwhile, some of the island’s best-known critics remained free, including veteran rights activist Elizardo Sanchez, Varela Project organizer Oswaldo Paya and Vladimiro Roca, son of the late Cuban Communist Party founder Blas Roca.

But all three reported they had been under heavy surveillance in recent days and said they would not be surprised if they were next.

“They are outside my house, on the corner,” Sanchez said by telephone late Thursday.

Paya and his colleagues collected more than 11,000 signatures of Cubans asking Fidel Castro’s government for a referendum on new laws guaranteeing civil rights such as free expression and private business ownership.

The Varela Project initiative, later shelved by the nation’s rubber-stamp parliament, also requested electoral reforms and amnesty for political prisoners.

The independent journalists also grew bolder in recent months, launching a new general interest magazine in a nation where virtually all media is state-controlled.

But American diplomats also grew more active, offering Internet access to journalists at the U.S. Interests Section here, inviting dissidents to receptions, and giving them radios and other material the government considered subversive.