Italy and Malta are refusing to allow a migrant rescue ship operated by the award-winning Spanish charity Proactiva Open Arms to enter their territorial waters, the NGO tweeted on Thursday.
"Italy and Malta are refusing to allow the ship Open Arms access to their territorial waters. The vessel has saved over 1,000 lives in a year in coordination with the Italian coastguard," read the tweet.
Italy's new populist government is taking a tough stance against charity migrant rescue boats in the Mediterranean and has turned two away from Italian ports this month with hundreds of Africans on board, sparking diplomatic standoffs with European officials.
One of the two boats, operated by the German charity Mission Lifeline, docked in Malta on Wednesday with 230 migrants on board after five days stranded at sea.
Malta said it would seize the boat pending an investigation of claims by Italy and Malta that Lifeline flouted international rules by refusing to cooperate with Libyan coastguard. The rescued migrants will be taken in by Malta, France, Ireland, Italy, Luxembourg and Portugal.
Mission Lifeline denies Italy and Malta's claims that it acted illegally and insists that its affairs are in order.
Malta's prime minister Joseph Muscat said the country had no obligation under international law to assist the ship, but was doing so on humanitarian grounds.