A United Nations envoy has published a scathing report on Cuba's treatment of political dissidents in prison.

The envoy, French judge Christine Chanet, was appointed by the UN High Commissioner for Human Rights to look into alleged human rights abuses.

Ms Chanet described reports that dissidents were being held in "trying" conditions as "particularly alarming".

More than 70 opponents of veteran leader Fidel Castro were arrested last April and handed lengthy jail terms.

The UN report also attacked the 40-year US trade blockade against Cuba.

It said it had "disastrous" consequences economically, as well as in the field of social and political rights.

Ms Chanet has not yet received permission to visit Cuba.

It has turned down an appeal by four Latin American countries for her to be allowed to go.

Havana said the UN commission should instead focus on conditions in Guantanamo Bay, the naval base in Cuba where the US imprisons and interrogates detainees from its "war on terror".