More than 200 African migrants are thought to have died when a boat carrying around 250 passengers sank in the Mediterranean Sea off the Libyan coast on Sunday night.
According to officials, the majority of the passengers were Africans and only 26 people have been rescued so far.
Al Jazeera quoted Libyan navy spokesman Ayub Qassem as saying: "There are so many dead bodies floating in the sea."
The under-equipped coast guard is said to be struggling to search for surviving passengers, who were attempting to illegally migrate to Europe.
In a separate incident on Saturday, a boat carrying Palestinians from Egypt to Europe capsized, killing at least 15 people.
Migration from Africa to Europe through the Mediterranean Sea has increased since 2011 due to unrest in Libya. The worsening security situation in the country has increased people-smuggling operations.
According to the UNHCR, more than 130,000 migrants have reached Europe by sea this year, with 118,000 of them landing in Italy.
In the last weeks of August, more than 300 deaths have been recorded in the Mediterranean Sea due to illegal crossings by migrants from North Africa to Europe.
In a major accident in August, a boat carrying at least 270 people capsized in the waters off Libya. The Libyan coastguard rescued 19 passengers while the rest are feared drowned. A UNHCR report says that 1,900 people have died in similar accidents so far this year, with 1,600 deaths occurring since June.