The International Organization for Migration says its Rome office has received a distress call from international waters in the Mediterranean about three boats in need of help.

The IOM says the caller reported 300 people on his boat with about 20 fatalities and said the boat was sinking. The caller provided no information on the other boats.

The IOM had no additional details, including the location of the distress call.

The distress call comes in the wake of what has been described as the largest migrant tragedy ever as some 900 people are believed to have died after the vessel they were on capsised.

An international aid agency spokeswoman has compared the scale of deaths in recent shipwrecks to the death toll in the sinking of the Titanic luxury liner more than a century ago.

Sarah Tyler, a spokeswoman for Save the Children in Catania, Sicily, said more than 1,000 people have died in the waters of the Mediterranean, adding "that is almost as many as died in the Titanic, and 31 times the number who died when the Costa Concordia sank."

One survivor's account has put at up to 950 the number of people on board the smuggler's boat that sank off the coast of Libya this weekend, with only a handful rescued. Last week more than 400 people died or went missing in another shipwreck.

The Bangladeshi survivor said many of the passengers were below deck and trapped inside when the boat sank.