A boat carrying more than 1,000 survivors of a highly organised, deadly attack by Islamic State-linked insurgents in northern Mozambique arrived in the port of Pemba on Thursday, a Reuters reporter and a diplomatic source said.

Aid workers were at the crowded port to give food to those disembarking from the green and white ferry, while police and soldiers kept control of crowds of people excited to see their relatives rescued after the attack that began last week in Palma, the reporter said.

The ferry docked at around 8am in Pemba, the provincial capital of Cabo Delgado.

A diplomatic source with direct knowledge of the rescue operation said there were roughly 1,200 people on board, including 300 children and 400 women. The source said all those on board were people displaced by the violence.

An official at the International Committee of the Red Cross said the government was screening those arriving at Pemba to prevent infiltration by armed groups.

Mozambique's government has confirmed dozens of deaths in Palma, including at least seven killed when militants ambushed vehicles trying to escape a besieged hotel. Witnesses have described bodies in the streets, some of them beheaded. However, the full scale of the casualties and displacement remains unclear.

As of Wednesday afternoon, a UN migration agency tracker showed more than 8,100 people had been displaced, almost half of them children. Roughly 20% had arrived in Pemba, with others turning up in the districts of Mueda, Montepuez and Nangade in Cabo Delgado.

Islamist insurgents have been increasingly active in the surrounding province of Cabo Delgado since 2017, though it is unclear whether they have a unified aim or what specifically they are fighting for.

The district where Palma is located is adjacent to natural gas projects worth $60bn (roughly R880bn). It is home to around 110,000 people according to UN estimates, of whom more than 40,000 sought shelter there after fleeing other attacks elsewhere.

Aid groups believe the attack has displaced tens of thousands of people, many of whom fled into dense forest or attempted to escape by sea. Hundreds, including many foreign workers, have been evacuated by air.

The fighting was continuing as recently as Tuesday, said security sources involved in rescue efforts and the UN, while Portugal is reportedly ready to send 60 soldiers to help train armed forces in Cabo Delgado.

Reuters has not been able to independently verify the accounts from Palma. Most means of communication to the town were cut off after the attack began last Wednesday. Phone calls to Mozambique's government and security officials went unanswered on Thursday.