HAVANA, March 14 (Xinhua) -- Cuba said on Thursday that the alleged "acoustic attacks" over the last two years on U.S. and Canadian diplomatic personnel on the island have been "manipulated" and "used for aggressive purposes" by Washington.

Carlos Fernandez de Cossio, director of U.S. affairs at Cuba's Ministry of Foreign Affairs, told a press conference on Thursday that the issue for the Caribbean nation is a matter of "national security."

He said Washington has spread the false accusation since February 2017 that U.S. staff in Cuba reported health symptoms such as brain damage, hear loss, nausea and instability due to alleged use of long-range acoustic equipment.

"We have no evidence this was generated to harm Cuba, but we categorically affirm there's a group of U.S. politicians and officials which have manipulated the issue and have tried to promote it to damage and rollback relations," Fernandez de Cossio said.

He said there is no evidence to support Washington's hypothesis, adding that the island hasn't had the proper collaboration and a fluid exchange with security agencies from the United States and Canada.

"We don't doubt some of these diplomats got sick, what we deny is the ailments and symptoms are the result of attacks in Cuba ... There are no reasons for any diplomat of any country to feel concerned for their health and safety in Cuba," he said.

Fernandez de Cossio said it is "striking and worrying" to see how Washington persists, two years later, in "ignoring repeated public questioning" of the theories about the possible causes of the conditions presented by the diplomats.

"There is no evidence, theory, or research result attached to science that justifies the use of the term attack which the U.S. government continues to publicly express, although it does not use it in the official exchanges that we have sustained," he said.

Fernandez de Cossio also said that Cuba takes the issue with "extreme seriousness" and has appointed its best experts to conduct investigations.

Members of an interdisciplinary investigation committee made up of more than 30 Cuban experts which have carried out the investigation for over two years also participated in the press conference.

The academics, government officials and scientists shared data, information, graphics and details of the ongoing probe.

Some Canadian diplomats have also experienced similar symptoms. Fernandez de Cossio said both nations have cooperated to find out the causes.

Over 20 U.S. diplomats and their family members reportedly showed symptoms such as hearing loss, tinnitus, vertigo, headaches and fatigue since late 2016. In response, U.S. President Donald Trump sharply reduced embassy staff in Havana, and expelled 15 Cuban diplomats in October 2017.