Spies first targets of Cuba attacks: report

The mystery behind a series of unattributed attacks on U.S. personnel in Cuba deepened Monday with a report that claimed spies were the first and hardest-hit targets.

The U.S. has claimed 21 diplomatic staffers were affected, but previously made no mention of intelligence officers being targeted.

Many of the initial victims were spies posted to the U.S.'s recently reopened embassy under diplomatic pretenses, according to a report by The Associated Press that cited a half-dozen unnamed officials.

The initial wave of attacks was heralded by victims who heard an "unsettling sound inside and in some cases outside their Havana homes". The spies suffered the worst affects, which included hearing loss and brain damage, which have not healed, the AP said.

But the attacks reportedly evolved, with more recent victims no longer hearing anything before falling ill, signaling a possible increase in the attacks' sophistication.

The U.S. on Friday made dramatic cuts to its diplomatic presence in Cuba and warned Americans to avoid travelling there, citing the attacks.

The U.S. embassy will have its staffing reduced to emergency personnel only, and visa operations have been suspended indefinitely.

Havana has pledged to continue investigating and the U.S. will assist in the effort, Secretary of State Rex Tillerson said last week when he announced the new measures.

The U.S. has not ruled out a third party could be behind the attacks, according to U.S. officials.

Commenting on the matter President Donald Trump said "some very bad things happened in Cuba.

"They did some bad things in Cuba," he said last week without naming the alleged culprit.

The U.S. had previously refrained from using the word "attack", instead calling them "incidents" until last Friday.

Cuba has denied any involvement in the matter.