Prominent Cuban dissidents on Tuesday called for an international forensic investigation into the death of a fellow regime opponent who they say was beaten to death.

Juan Wilfredo Soto, 46, died Sunday in the central city of Santa Clara, according to Elizardo Sanchez, who leads the Cuban Human Rights and National Reconciliation Committee.

The Americas' only one-party Communist government denies that Soto was beaten. Government employed doctors say he died of pancreatitis.

A group led by Guillermo Farinas, a Sakharov prize winner, called for a "public and transparent investigation of the case, carried out by internationally renowned forensic experts who are not employed by the Cuban government."

The group, which also includes Elizardo Sanchez, Hector Palacios, Gisela Delgado, Rene Gomez, Felix Navarro and Ivan Hernandez, said the government had to prove its claim.

The United States said on Monday that it was "very concerned" about Soto's death.

Farinas, who lives in Santa Clara, said Soto died after he was taken to hospital following his arrest in a park and subsequent beating.

"There is not the slightest doubt that there was a cause and effect, and that Soto's death was related to the beating he was given," after refusing to leave the city's central park, Farinas said shortly after the activist died.

Soto's death came 15 months after the February 2010 death of dissident demonstrator Orlando Zapata, who died on a hunger strike protesting prison conditions, drawing an international outcry.