Rescuers are searching for hundreds of migrants in the Mediterranean after a boat carrying as many as 700 people capsized off the coast of Libya on Wednesday, Aug 5, BBC News reports.

The Irish navy said "significant loss of life" was feared and Medecins Sans Frontieres confirmed "many deaths". But the Italian coast guard and the UN refugee agency say 400 people have been rescued and 25 bodies recovered so far.

More than 2,000 migrants are said to have died in 2015 trying to cross the Mediterranean to reach Europe.

Wednesday's incident occurred when the packed fishing boat ran into rough weather about 15 miles (25km) from the Libya's coast.

A distress call was picked up in Sicily and one of the first ships on the scene was an Irish navy vessel. But as she launched her boats, the migrants apparently moved to one side of the fishing boat, causing it to capsize.

At least three other ships and three helicopters were reported to have arrived in the area shortly afterwards to help with the rescue.

MSF said its Dignity I vessel was at the scene and two more of its boats were on their way to the area.

"The team on the #Dignity1 can confirm that there have tragically been many deaths but does not have figures at this stage," MSF said in a tweet.

Earlier this week, the ION warned that the number of migrants attempting to cross the Mediterranean is much higher than in the same period last year.

"It is unacceptable that in the 21st century people fleeing from conflict, persecutions, misery and land degradation must endure such terrible experiences [...] and then die on Europe's doorstep," IOM director general William Lacy Swing said in a statement.