One of Cuba's only independent think tanks said Monday that it is closing because of pressure from what it described as powerful institutions on and off the communist island, though it gave no details.

Cuba Posible was founded in 2014 with the aim of publishing work by analysts and intellectuals who wanted gradual reform in Cuba and didn't subscribe to the push for regime change promoted by U.S.-backed dissidents. Still, the think tank's founders were harshly criticized online by government-allied forces who described them as a foreign-backed third column seeking government overthrow by other means.

While the group's founders and members never publicly discussed other forms of pressure, the Cuban state employs a wide range of tactics including threats and harassment against perceived government opponents.

The think tank said in a written statement that it was targeted by "all the mechanics and methods of powerful institutions, in Cuba, where we work, and off the island, where we've tried to guarantee the minimal conditions needed to allow our work."

Project co-director Lenier González confirmed the authenticity of the statement but declined to elaborate on any aspect of the pressure that the group said it had received.

González and his partner, Roberto Veiga, published articles online and organized conference around themes such as economic reform, poverty, development and migration. Cuba does not officially allow non-state media to exist but has generally tolerated a small number of independent outlets publishing online.

The country similarly does not allow the type of independent think tanks or advocacy groups common in most other countries, although a handful have been allowed to operate in recent years.

"The Cuban public sphere on and off the island is losing out with the silencing, whether it's temporary or permanent, of a project aimed at opening the boundaries of thought, something that's more difficult in tense political environments," said Arturo López-Levy, a professor of international relations at Gustavus Adolphus University in Minnesota who published a series of articles through Cuba Posible.

Cuba's domestic dynamics have become considerably tenser with the ramping up of pressure from the U.S. and a cash shortage brought about largely by a decline in aid from Venezuela. The Cuban government allowed an independent animal-rights march last month but forbade an independent gay-rights parade, and briefly arrested some of the participants.