SAN JUAN, Puerto Rico — Ralph Gonsalves, the prime minister of St. Vincent and the Grenadines, was hospitalized after a demonstrator threw a rock at his head during an anti-vaccine protest in the eastern Caribbean island, officials said late Thursday.

Gonsalves was bleeding profusely but is expected to recover, according to a statement from his office.

Authorities said Gonsalves was injured when he stepped out of his car and tried to walk into Parliament amid a crowd of some 200 people that had blocked the entrance as they set roadblocks on fire.

“Such an act is to be unequivocally condemned,” his office said.

The attack was criticized by others including Ronald Sanders, ambassador to the Organization of American States.

“This development in Caribbean politics is reprehensible,” he said.

Local media quoted Senator Julian Francis saying that an unidentified woman had been arrested. No further details were immediately available.

The crowd had gathered to reject proposed measures to fight COVID-19, although Gonsalves clarified that he would not make vaccines mandatory.