Havana (AFP) - Five years after it was closed due to mysterious "sonic attacks" on diplomatic staff, the US consulate in Havana on Wednesday resumed full immigrant visa services for Cubans.

The reopening came amid a record exodus from the communist island to the United States, mainly by undocumented migrants, as Cuba suffers its worst economic crisis in 30 years.

Cubans, many of whom had been waiting for years, rejoiced at the new ease of access. Since 2017, they have had to travel at great cost to a third country, usually Guyana in South America, to submit visa requests.

"Everything went very fast," said Melissa Vazquez, 18, after putting in her application. She had been waiting seven years to be reunited with her father in the United States.

The US embassy last week said it sought to "ensure safe, legal and orderly migration of Cubans by expanding consular operations in Havana" and resuming immigrant visa processing.

Tourist visas remain off limits for now.

The consulate was also resuming the Cuban Family Reunification Parole Program, which allows islanders who qualify to join relatives in the United States without an immigrant visa.

The consulate was closed under the administration of then-president Donald Trump after diplomatic staff and their families fell ill with symptoms later nicknamed Havana Syndrome.

US missions in other countries also subsequently claimed to have been targeted, but the exact nature of the alleged attacks remains a mystery.

No warming

Since President Joe Biden replaced Trump in 2021, several high-level meetings have sought to find a solution to the migratory standoff.

In May last year, the consulate resumed "limited" visa services.

"It is a good sign that the governments of both countries are talking to each other about how to manage migration flows in an orderly and rational way," said analyst Michael Shifter of Georgetown University in Washington.

Jorge Duany, Cuba specialist at Florida International University, said the talks were "limited to migration issues" and did not indicate a general warming of ties.

Washington has had sanctions against Cuba for 60 years.

After a four-year relaxation under president Barack Obama, relations deteriorated under Trump, who reinforced sanctions.

Despite election promises, Biden has not reversed the measures, even hardening his tone following anti-government protests in July 2021 that saw hundreds arrested and jailed.

The Biden administration has kept Cuba on its list of countries deemed sponsors of terrorism and recently added it to another of countries undermining religious freedom.

In Washington, State Department spokesman Ned Price said the renewed visa processing "makes real what we have consistently said -- that we seek to find practical ways to support the Cuban people."

He said Washington has returned staff to Havana as it believes it can "mitigate the risks" from the mysterious health incidents, which remain officially unexplained.

Cuba's deputy foreign minister, Carlos Fernandez de Cossio, said on Twitter that "to stop or substantially reduce irregular migration to the US, the government ... must abandon efforts to make life miserable for Cubans."

Cuba was hard hit by the coronavirus pandemic, which crippled its critical tourism sector.

Remittances sent from abroad, a vital source of income for Cubans that in 2019 reached $3.7 billion, also largely dried up.

"There is a direct link between the upsurge of extreme (US) measures against the Cuban economy and the dramatic migratory flow," Johana Tablada, senior official in Cuba's foreign ministry, said in November.

Last year, Washington issued more than 20,000 visas to Cubans. More than 277,000 Cubans entered the United States illegally in the 12 months from December 2021, according to American authorities.

In 2021, during the pandemic, the number was just 39,000.

Departures shot up since November 2021, when Cuba ally Nicaragua eliminated visa requirements for islanders, meaning many would-be migrants now fly to the Central American country to start the dangerous trek on foot to the United States.

By resuming visa services, "Biden is trying to recalibrate his policy towards Cuba, seeking a middle way between Trump's 'maximum pressure' and Obama's 'rapprochement,'" said Duany.

"But for the time being the changes in American policy towards the island have been minimal," he added.