By Sheena McKenzie and Livia Borghese, CNN

(CNN) -- More than 200 migrants died attempting to cross the Mediterranean over the weekend, while four rescue ships remain docked in European ports, raising fears of more deaths in the coming months.

A total of 218 migrants are believed to have drowned in two separate shipwrecks on Friday and Sunday, according to International Organization for Migration (IOM) spokesman Flavio Di Giacomo.

Among the dead were three babies, dressed in brightly colored clothing and looking almost as if they were sleeping. They were carried ashore to Libya on Friday.

It brings the total number of migrants dying while crossing the Mediterranean to 1,400 this year, according to Di Giacomo.

In the weekend's shipwrecks, 32 migrants were rescued by the Libyan Coast Guard and returned to Tripoli.

But as the tragedies unfolded, four rescue ships run by various nongovernmental organizations remained docked at European ports, unable to sail the high seas because of legal restrictions.

Now the NGOs have warned that unless they are able to return to open waters soon, migrant death tolls will continue to rise.

It follows weeks of wrangling between European countries over whether to allow NGO rescue ships carrying hundreds of migrants to dock in their ports.

As of Tuesday, the following rescue vessels remained docked:

Lifeline -- Is detained in Malta "pending the necessary investigations according to national and international rules," the Maltese government said in a statement Thursday. The German NGO ship, which picked up 234 people and 17 crew members off the coast of Libya in late June, was forced to drift in the Mediterranean for days as European countries bickered over responsibility, before it eventually docked in Malta.

Seefuchs -- Is docked in Malta while authorities investigate the ship's flag status. The ship is run by German NGO Sea-Eye.

Sea-Watch 3 -- Is detained in Malta "without any legal ground provided by authorities," according to the German NGO. CNN reached out to Maltese authorities for comment but had not heard back at the time of publishing.

Aquarius -- Is docked in Marseille following a regularly scheduled port call. "Given the current politics at sea, and the criminalization of NGO search & rescue vessels, we force ourselves to also take some time to assess the situation," it tweeted on Tuesday. The vessel, run by aid group Doctors Without Borders, or Médecins Sans Frontières (MSF), made headlines last month after it rescued more than 600 migrants but was forced to drift in the Mediterranean for days after both Italy and Malta refused to allow it to dock. Spain eventually took it in.

A fifth rescue ship, the Open Arms, operated by the Spanish NGO Proactiva Open Arms, was on Tuesday traveling to Barcelona carrying 60 migrants rescued off the coast of Libya over the weekend.

Pia Klemp, captain of the Sea-Watch 3, which is docked in Malta, said the boat was well equipped and ready to help those stranded at sea. But unless his vessel was freed, he warned that the death toll would continue to rise.

"While we are hindered from leaving port, people are drowning, this is absolutely unacceptable. Any further death at sea is on the account of those preventing rescue from taking place," he said in a statement Monday.

"How many more shipwrecks will it take before Europe, once again, realizes that saving lives at sea must remain non-negotiable?"

Similarly, IOM spokesman Giacomo said that while the number of migrants crossing the Mediterranean and arriving in Europe had fallen in comparison to previous years, the rising death toll was still "worrying."

"It is necessary to reinforce the patrol of the international waters, weakened by the absence on the NGO vessels," Di Giacomo told CNN.

Days after EU migrant deal, dozens die

The migrant deaths come just days after European Union leaders hailed a new deal that could prevent more migrants from making the Mediterranean crossing -- if it can be made to work.

Under the deal, struck in the early hours of Friday, the burden of resettling refugees will be shared more widely among member states. EU leaders agreed -- but only on a voluntary basis -- to set up migrant processing centers within Europe that would distinguish between genuine asylum seekers and "irregular migrants, who will be returned."

The EU will also look into setting up migration centers in countries outside Europe, such as in North Africa, with the aim of breaking the business model of human traffickers who ship migrants across the sea to Europe.

However, it's not yet clear whether Libya and other North African nations are willing or able to set up such a system. Libyan deportation centers are rife with abuse, rights groups say, and a CNN undercover investigation last year revealed cases of migrants being sold at slave auctions.

Indeed, MSF urged EU leaders Friday to "show some basic decency" by committing to search-and-rescue operations for those in trouble at sea -- and then taking them to a place of safety, rather than Libya.

"EU member states are abdicating their responsibilities to save lives and deliberately condemning vulnerable people to be trapped in Libya, or die at sea," said Karline Kleijer, head of emergencies for the aid group.

"They do this fully aware of the extreme violence and abuses that refugees and migrants suffer in Libya."

European standoff; migrants left in limbo

Meanwhile, relations between EU member states Italy and Malta have become strained in recent weeks following several standoffs over allowing nongovernmental organizations' rescue ships carrying hundreds of migrants to dock in their ports.

The standoff over the Lifeline -- and others like it, including those involving the rescue ship Aquarius and a Maersk cargo ship -- have exposed the tough new policies of Italy's hardline interior minister and leader of the anti-immigration League party, Matteo Salvini.

Salvini has been critical of NGO ships rescuing migrants from the Libyan coast and continuing to deliver them to European shores. Instead, he has pushed for greater responsibility to fall on the Libyan Coast Guard to rescue the migrants and return them to the African continent.

Indeed, as the Lifeline drifted in limbo last month, Salvini traveled to the Libyan capital Tripoli, meeting the interior minister and praising the country's coast guard for rescuing 820 other migrants and returning them to Libya.

Italy has also supplied Libya with the maritime power to continue its work, on Monday agreeing to donate 10 patrol vessels to the Libyan Coast Guard, the Italian transport minister said in a statement.

So far this year, some 42,000 migrants have crossed the Mediterranean to Europe, according to the UN Refugee Agency (UNHCR). It's a drop since peak 2015 levels when more than a million made the journey.

But as this weekend shows, migrants are still dying by their hundreds every week.