The United States Centers for Disease Control and Prevention said it raised COVID-19 related travel warnings for Malta, Moldova, Sweden and Argentina.

For Malta, Moldova and Sweden, the travel warning was raised to level four or "very high" while for Argentina, it was raised to level 3 or "high", the CDC said on Tuesday.

For level four countries, the US CDC warns American travellers to avoid these destinations. "If you must travel to these destinations, make sure you are fully vaccinated before travel," the CDC says.

Malta has registered a sharp rise in the number of Covid-19 cases, with nearly 1,300 reported on Tuesday.