A boat carrying hundreds of migrants has capsized in the Mediterranean.
The incident occurred about 25 miles off the Libyan coast when the overcrowded vessel got in to difficulty sparking a major search and rescue operation.
The International Organisation for Migration (IOM) said they had received reports that as many as 700 migrants had been on board.
The Irish Navy ship LE Niamh was sent to the scene at the request of the Italian coast guard while the MV Dignity I, a vessel operated by Medecins Sans Frontieres was also at the scene along with a boat from the Migrant Offshore Aid Station Moas, based out of Malta.
The #LÉNIAMH is still deployed 110 km's NW of Tripoli with 363 rescued persons onboard (340 male, 10 female, 13 children) and 25 deceased— Irish Defence Forces (@defenceforces) August 5, 2015
"We think that there could have been up to 700 people on board," an IOM spokesman said.
The agency said it was receiving reports of a "significant number" of casualties.
Scores of others are believed to have been pulled from the water alive.
Only days ago the IOM warned the death toll of migrants trying to cross the Mediterranean this year had reached 2,000 compared with 3,279 for the whole of 2014.
Defence Minister Simon Coveney confirmed that the LÉ Niamh is currently involved in the rescue operation off the Libyan coast and was the first ship at the scene.
"At 8 am Irish time, the LÉ Niamh was tasked by the Italian Marine Rescue Co-Ordination Centre (MRCC) to come to the assistance of a fishing vessel north-west of Tripoli, which was in distress with an estimated 600 persons on board," Minister Coveney confirmed.
BREAKING: This is the scene of today's catastrophe where at least 25 men, women and children have died. pic.twitter.com/K3G7G9o6nX— MSF Sea (@MSF_Sea) August 5, 2015
"The LE Niamh, along Italian Naval vessels, the Medicins Sans Frontiére vessel “DIGNITY”, and a number of helicopters are currently engaged in the rescue operation.
"All assets including RHIBS (rigid hull inflatable boats) and life rafts have been deployed in support of the emergency operation.
"As the operation is currently ongoing, with all personnel fully engaged in the rescue, it is difficult to ascertain full details on the scale of the incident," he continued.
"However I understand that the fishing vessel capsized and that the loss of life is likely to be significant.
"The crew of the Niamh are working flat out with their counterparts to rescue as many as possible.
"Latest reports from LÉ NIAMH are that 165 people have been rescued.
"Tragically seventeen bodies have also been recovered. That number is likely to rise in the coming hours”.
“Our thoughts and prayers are with all those who have lost their lives, the survivors and the rescuers for whom this is an extremely difficult operation”, the Minister added.
A Medecins Sans Frontieres spokesman told Independent.ie that its rescue boat the Dignity is also on the scene.
"According to information currently available, there could have been up to 700 people on board at the time of the incident.
"MSF’s two other search and rescue vessels in the Mediterranean- the MY Phoenix (operated in collaboration with the NGO MOAS) and the Bourbon Argos are also moving to the zone of the shipwreck to offer assistance."
Juan Matías, MSF project coordinator on the Dignity I later reported on what he described as a "horrific sight".
"People were desperately clinging to lifebelts, boats and anything they could, fighting for their lives, amidst people drowning, and those who had already died.
“The fact that we were first called to assist this boat and then shortly afterwards sent to another one highlights the severe lack of resources available for rescue operations," he said.
Other rescue ships continued to arrive to the area to assist, and the Dignity I provided medical treatment to ten people.
Five were in such severe condition that they needed to be evacuated by helicopter.