Pemba (Mozambique) (AFP) -
The key northern Mozambique town of Palma was all but deserted on Monday, its residents fleeing by road, boat or on foot as the Islamic State (IS) group claimed control after a prolonged onslaught.
IS-linked militants attacked the town on Wednesday, escalating an Islamist insurgency that has spread steadily across northern Mozambique since 2017.
Dozens of people have been killed in the large-scale attack -- the closest yet to a multi-billion-dollar gas project being built 10 kilometres (six miles) away by France's Total and other energy giants.
'The caliphate's soldiers seized the strategic town of Palma,' IS said in a statement posted on its Telegram channels.
The town of 75,000 people in Cabo Delgado province was all but emptied of its population, said civil society activist Adriano Nuvunga.
'The violence has ceased, but it is believed some of the insurgents have pulled back and some are still around in hiding,' he told AFP.
Many survivors said they had walked for days through forest to seek refuge in Mueda, 180 kilometres (112 miles) to the south, where they arrived limping on swollen feet.
'Many people fell from fatigue and were unable to continue walking, especially the elderly and children,' said one escapee in Mueda who did not wish to be named.
Some survivors fled to the gas project site, from where they are being sent to the regional capital Pemba via boat.
The government said dozens were killed in the coordinated militant attack, including seven people caught in an ambush during an operation to evacuate them from a hotel where they had sought refuge.
A South African is among those killed, his family said.
'Attacks started shortly after a large ship with food had just arrived,' one escapee told AFP via an online message, referring to food aid deliveries to the farthest northern coastal town.
'They attacked the city and brought trucks to carry the food.'
Assailants fired on civilians in their homes and on the streets 'as they tried to flee for their lives', according to Human Rights Watch (HRW).
Witnesses told AFP they first targeted banks and the police station before descending on the rest of the town.
- Boatloads of survivors -
Thousands of escapees were arriving on boats on Monday in Pemba, the provincial capital around 250 kms to the south, according to sources there.
International aid agency sources said between 6,000 and 10,000 people were waiting to be evacuated.
The attack forced expatriate workers and locals to seek refuge temporarily at a heavily guarded gas plant located on the nearby Afungi peninsula.
Sea Star, a large passenger vessel, arrived in Pemba on Sunday with around 1,400 people, mostly workers including Total employees.
Another ship arrived in Pemba on Sunday afternoon and was released on Monday morning, according to an official from an international aid agency operating in the city.
UN agencies were due to hold emergency talks to coordinate the evacuation and humanitarian aid for the new arrivals.
Pemba is already packed with hundreds of thousands of other people displaced by the Islamist insurgency, which has uprooted nearly 700,000 from their homes across the vast province.
The defence ministry said late Sunday the security forces had 'reinforced their operational strategy to contain the criminal attacks of terrorists and restore normality in Palma, having carried out operational actions focused primarily on the rescue of hundreds of citizens in the last three days.'
In Portugal, Prime Minister Antonio Costa said his government was monitoring the situation 'great concern,' adding that he had been in touch with President Filipe Nyusi.
- Ruthless campaign -
The violent, calculated raid broke a three-month hiatus in Islamist attacks widely attributed to counter-insurgency tactics and the January-March rainy season.
Although the extremists launched their campaign in 2017, experts say they began mobilising a decade earlier as disgruntled youths started to practise a stricter form of Islam, upset over locals drinking alcohol and entering mosques dressed in shorts and shoes.
Their bloody campaign has claimed at least 2,600 lives, half of them civilians, according to the US-based data-collecting agency Armed Conflict Location and Event Data (ACLED).
The insurgents are known locally as al-Shabaaab, although they are not believed to have links with the Somali jihadist organisation by that name.
The US State Department this month said the group reportedly pledged allegiance to IS in April 2018. It named its leader as Abu Yasir Hassan, and blacklisted him.