(CNN) -- At least 17 people were killed when a ship carrying migrants sank Monday about 100 miles off southern Italy, the Italian navy said Tuesday.
Just over 200 other people who'd been on the ship were rescued, the navy said.
The incident came a day after a boat carrying illegal migrants sank off the coast of Tripoli, Libya, killing at least 40 people, according to an account from Libya's Interior Ministry.
Southern Italy -- especially tiny Lampedusa, which is the closest Italian island to Africa -- is a frequent destination for refugees seeking to enter European Union countries from Africa. Migrants often pack into unseaworthy and ill-equipped boats, and shipwrecks off Italian shores are common.
The Italian military has rescued about 2,000 migrants in the last five days alone, Italy's navy said Monday, highlighting the difficulty in keeping up with the flow of migrants seeking to reach European soil.
Tens of thousands of people are rescued from the Mediterranean Sea each year, according to the European Union border agency, Frontex.
The U.N. refugee agency, UNHCR, expressed its dismay Tuesday over the rising number of migrants dying as they try to make the perilous crossing.
UNHCR spokesman Adrian Edwards told reporters that those who lost their lives Monday include 12 women, three children and two men.
In addition, 121 people are believed to have died in three separate boat accidents off the Libyan coast over the past two weeks, he said.
Some of the 53 survivors of a shipwreck off Libya on May 6 told the UNHCR that the smugglers pushed them onto the boat and set off even though the boat was damaged in the middle, Edwards said. It's believed 77 people drowned in that incident.
The deaths of more than 300 African migrants in a shipwreck off Lampedusa last October shocked Italy and the world, and led to calls for EU lawmakers to review their migration policies.
A rescue operation established by the Italian government after that tragedy saved more than 20,000 people at sea through early April, the United Nations refugee agency said. Nearly 43,000 migrants arrived in Italy by sea in 2013, according to the agency.
Many of the migrants are from African nations, while others have fled war-torn Syria.
The UNHCR believes more than 170 migrants have died at sea trying to reach Europe so far this year.
It praised rescue efforts by the Italian and Libyan authorities, as well as private boats, but said more still needs to be done.
"We also urge governments around the world to provide legal alternatives to dangerous sea journeys, ensuring desperate people in need of refuge can seek and find protection and asylum," the agency said. "These alternatives could include resettlement, humanitarian admission, and facilitated access to family reunification."
CNN's Lindsay Isaac contributed to this report.