The Italian coastguard began a search for survivors Saturday after a vessel carrying migrants capsized off the Mediterranean island of Lampedusa overnight.

Officials said in a statement that the craft had overturned as the coastguard was bringing migrants aboard its own boats off the island located between Sicily, Tunisia and Libya.

While around 40 people were saved, survivors of the accident said five were missing from the original number aboard.

The coastguard said a helicopter had been sent to search for any more still at sea.

Officials did not specify where the migrants had come from.

The overnight operation had followed "an especially intense day, as a large number of vessels carrying migrants was reported" on Friday, the coastguard said.

Other vessels carrying migrants are also reported to be in distress at sea: migrant rescue hotline Alarm Phone said on Friday that two separate boats carrying a total of more than 150 people were adrift at sea. 

Malta's Armed Forces did not respond to a request to comment on that claim. Meanwhile, Maltese police arrested eight men who are believed to have reached Malta from North Africa by boat late on Friday. The men were found walking from Żurrieq to Għar Lapsi.