内容摘要："[The movement's] officials, who are hardened activists, enter into a relationship with the local authority… Social norms – the veil, beards, dress, fasting - are gradually imposed as the ecosystem solidifies," the authors write.

"[The movement's] officials, who are hardened activists, enter into a relationship with the local authority… Social norms – the veil, beards, dress, fasting - are gradually imposed as the ecosystem solidifies," the authors write.

Our analysis of the imagery shows significant development at one of the sites in south-west Gaza, close to the ruins of a village that is now an Israel Defense Forces (IDF) base.Satellite photos since early April show the construction of a road there and a large staging area, surrounded by berms - large defensive barriers made of piled sand or earth - about 650m (2,130ft) from the border with Egypt.

A high-resolution image captured on 8 May shows bulldozers and excavators working on a section of land spanning about 20 acres (8 hectares). IDF armoured vehicles are at a fortified building nearby.A photo taken on site, geolocated by BBC Verify, also shows lighting being installed on the perimeter.Further imagery from 11 and 12 May shows this, along with three other sites, continuing to expand. One site is about half a kilometre from a collection of eight UN warehouses, and 280m from another large warehouse.

Stu Ray - a senior imagery analyst with McKenzie Intelligence - agreed the sites were likely to be secure distribution centres. He noted that some of the facilities are in "close proximity to IDF Forward Operating Bases which ties in with the IDF wishing to have some control over the sites".Analysts with another intelligence firm, Maiar, said the facilities appeared to be designed with separate entrances for trucks to move in and out, and with other gaps in the berms that would be suitable for pedestrian entrances.

The IDF did not comment on the potential aid centres when approached by BBC Verify, but said that its operations in Gaza were carried out "in accordance with international law". Cogat - the Israeli body responsible for managing crossings into Gaza - did not respond to a request for comment.

Three of the four sites located by BBC Verify are south of the IDF's newly created Morag Corridor.In another incident on Tuesday, a paramedic said his ambulance was shot at by an Israeli drone while he was transporting staff and food between al-Awda and Kamal Adwan hospitals.

Khaled Sadeh said he was with another ambulance when bullets hit both vehicles' windshields. Nobody was injured.Dr Salha shared photos of the ambulances and confirmed that Mr Sadeh was unable to return to al-Awda because of the threat of Israeli fire.

The BBC supplied details of the allegations and photos to the IDF, but it said it "could not confirm" the reports.Hospitals and medical personnel are specially protected under international humanitarian law.