Last week’s migrant death toll in the Mediterranean Sea is believed to be the biggest this year as 1,083 migrants are estimated to have died or gone missing in nine separate accidents, according to the International Organization for Migration (IOM).

The largest of nine accidents occurred on May 26, about 35 nautical miles north of Zuwara, Libya, in which around 500 migrants disappeared, including 40 children, IOM reports.

Particularly dangerous is the Central Mediterranean route between North Africa and Italy. Since the beginning of 2014, the route has seen 27 percent of sea arrivals to Europe but accounts for 85 percent of migrant deaths in the Mediterranean during the same period. For every fifty migrants having attempted to cross it, one has died en route.

In addition, there is a stark difference in the number of bodies recovered from the water depending on the route. Specifically in 2016, 80 percent of the bodies of those who perished in the Eastern Mediterranean have been recovered, while less than ten percent have been recovered in the Central Mediterranean.

Moreover, the Mediterranean currently accounts for almost 90 percent of recorded migrant deaths around the word so far in this year.

Commenting on the last week’s death toll, UN Secretary-General Ban Ki-moon called for a comprehensive and collective response to large movements of refugees and migrants, including expanded legal pathways.

“While the Secretary-General commends the brave efforts of the joint Italian and European search and rescue operations, he calls on concerned governments and organizations to redouble their efforts to save those at risk at sea and to counter the migrant smuggling and human trafficking networks in the Aegean and Mediterranean Seas,” the statement said.

In comparison, some 1,855 died in the crossing in the first five months of 2015 and 57 of 2014. So far this year, 203,981 people have made the journey in the Mediterranean, the UN refugee agency said.

“The odds of being among the dead are currently one in 81,” William Spindler, spokesperson for the Office of the UN High Commissioner for Refugees (UNHCR) said.

What is more, the majority of boats departing Libya are at present reported to be leaving from Sabratah area to the west of Tripoli. They remain more crowded that those that have been normally seen on the Turkey-Greece route, often carrying 600 or more passengers, and sometimes being towed by larger fishing boats, according to UN.

Spindler says that such data highlight the importance of rescue operations as part of the response to the movement of refugees and migrants in the Mediterranean. He also sees the need for real, safer alternatives for people needing international protection.