Rabat condemned its neighbour's "inhumane behaviour" towards the migrants who included "women and children in a very vulnerable situation".
The expulsion was "contrary to the rules of good neighbourliness advocated by Morocco", it added.
A statement from the Moroccan foreign ministry late Saturday expressed "deep concern" at the situation, and said Algeria "must meet its political and moral responsibility" towards the migrants.
It said they had crossed from Algerian territory and then tried to enter Morocco.
An NGO official in Figuig, who requested anonymity, said the Syrians were still stuck at the border on Saturday without access to water or food.
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The expulsion was "contrary to the rules of good neighbourliness advocated by Morocco", it added.
A statement from the Moroccan foreign ministry late Saturday expressed "deep concern" at the situation, and said Algeria "must meet its political and moral responsibility" towards the migrants.
It said they had crossed from Algerian territory and then tried to enter Morocco.
An NGO official in Figuig, who requested anonymity, said the Syrians were still stuck at the border on Saturday without access to water or food.
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