"We have already flown 140 illegal migrants back home in Senegal this morning and we are preparing a flight of 140 others also to Senegal soon from Oujda," a senior official said.
He and other officials said a total of 365 Senegalese would be deported by plane on Monday and over the next few days.
They added that 600 people from Mali would be deported within the next few days.
Moroccan Junior Foreign Minister Taieb Fihri met Senegalese Foreign Minister Abdou Malal Diop on Monday and then Mali's minister in charge of expatriates, Dicko Omar Hamadoun, over deportations, state news agency MAP said.
Fihri said, in remarks carried by MAP, Rabat "will not tolerate the illegal presence on its territory" of immigrants.
Oujda is 540km east of Rabat and is an entry point for illegal immigrants from Algeria.
Immigrants were cuffed and
taken south from Bouarfa
"Morocco has agreements with Mali and Senegal allowing Rabat to deport illegal migrants to these two countries," said a senior government official.
"Morocco alone is paying for these deportations and does not receive aid from outside," he added.
The officials gave no further details about the deported immigrants, but rights activists said they were among 1500 left by the Moroccan authorities in the desert last week before they managed to trek back to camps in the Feguig area.
The authorities' action was reported by the medical aid organisation Medecins Sans Frontieres, which said it had discovered hundreds of people, including pregnant women and children, who said they were rounded up by Moroccan forces and abandoned in the desert.
The immigrants, most from sub-Saharan Africa, had been escorted by the Moroccan authorities in buses from the north of the kingdom, where they had been trying to enter Spain illegally.
Hundreds of sub-Saharan Africans have in recent weeks stormed Spanish North African outposts of Ceuta and Melilla, the only EU territory in Africa.
Madrid and Rabat have responded by sending troops to the frontier, and Spain has deported some of the new arrivals back to Morocco, a move denounced by humanitarian groups.
UN Secretary-General Kofi Annan has urged the two governments to treat the immigrant groups humanely. The European Union and United Nations are sending teams to Morocco amid growing concern about how the authorities are treating immigrants.
The UNHCR wants to speak to
immigrants from conflict zones
Francesca Fontanini, spokeswoman for UN refugee agency UNHCR, was with a UNHCR delegation that visited a holding centre for immigrants in Melilla.
"We are interested in speaking to the people who have come to Melilla from countries where there are conflicts such as Ivory Coast, Sudan, Congo, Liberia or Sierra Leone to see if there is a possibility of political asylum," she said.
On Friday, Moroccan Communications Minister Nabil Benabdallah responded to criticism of Rabat's treatment of the immigrants by saying it was respecting human rights.
Rights activist Kabouri Seddik said on Monday: "They bused most of the migrants to Oujda starting late on Sunday. Some buses left Bouarfa early this morning. Just 150 migrants were still in one of two Bouarfa's camps."
Seddik, a senior official at the independent Moroccan Human Rights Association, said local authorities had told him they had taken the migrants to Oujda, where there was an airport, to be flown home.