The number of women killed in Argentina has reached a 10-year high under coronavirus lockdown, a leading rights group said on Monday, with more than 50 femicides in less than two months.

Three of those women were murdered in just the last four days, according to La Casa del Encuentro, a Buenos Aires-based feminist group that said not only the numbers but the severity of the violence was hugely concerning.

"We're very worried. It's the highest number in 10 years," said Ada Rico, the group's president and director of the organization's Femicide Observatory watchdog project.

"(Women) are being beaten to death or strangled," she told the Thomson Reuters Foundation.

Twelve women are killed every day in Latin America because of their gender in a crime known as femicide, according to the United Nations, and the region is home to 14 of the 25 countries with the highest rates of femicide in the world.

The vast majority of killings go unprosecuted.

The data in Argentina follows a worldwide trend of rising gender-based violence under lockdown that has left women trapped at home with their abusers and unable to seek help while tensions due to COVID-19 escalate, experts say.

"She's isolated with the person who's attacking her," said Rico. "Sometimes when a woman's locked up, she can't make a phone call."

Along with the three most recent deaths, at least 49 women were killed between March 20 and May 14, the group said. That is up from 40 in the same period last year and an increase of nearly a third compared with 2018.

Calls to Argentina's emergency 137 line for domestic abuse victims increased by two-thirds in April versus a year earlier after shelter-in-place measures were ordered in mid-March.

U.N. Secretary General Antonio Guterres has called on governments to take urgent measures to tackle a "horrifying global surge" in domestic violence, adding that for many women, being in their own homes was often the most dangerous.

Argentina has recorded more than 7,800 confirmed coronavirus cases and about 360 deaths, according to a Reuters tally.

The number of femicides was calculated using local media reports, Rico said.