Bahrain has approved Johnson & Johnson's one-dose COVID-19 vaccine for emergency use, the first country to do so, the National Health Regulatory Authority (NHRA) said on Thursday.

The small Gulf state already offers citizens and residents free of charge four vaccines: the Pfizer/BioNTech, vaccine, one manufactured by Chinese state-backed pharmaceutical giant Sinopharm, the Oxford-AstraZeneca COVID-19 vaccine and Russia's Sputnik V.

NHRA said the vaccine was for groups at greater risk of developing complications from COVID-19, including the elderly and people with chronic diseases.

"An in-depth study had been conducted on all documents submitted by the company, which included the results of the clinical trials conducted," NHRA CEO Mariam Al-Jalahma said.

The U.S. Food and Drug Administration said on Wednesday the Johnson & Johnson shot appeared safe and effective in trials, paving the way for its approval for emergency use in the United States as soon as this week.

(With input from agencies)