CAIRO (Reuters) - Egyptian security forces have committed widespread abuses against civilians in northern Sinai, some of which amount to war crimes, Human Rights Watch (HRW) said on Tuesday.

Egypt’s ground and air forces last year launched a major operation in Sinai to crush Islamist militants behind a wave of attacks against civilians and security forces. President Abdel Fattah al-Sisi ordered the operation after gunmen killed hundreds of worshippers at a Sinai mosque months earlier.

The HRW report accused security forces of arbitrary arrests including children, torture, extrajudicial killings, collective punishment and forced evictions.

An Egyptian military spokesman denied the report, saying it was based on undocumented sources.

“The armed forces take into consideration the lives of civilians while implementing military operations against terrorist elements by conducting air raids outside population centers,” the military said in a statement.

New York-based HRW said its 134-page report was researched from 2016-2018 and based on interviews with 54 North Sinai residents and former government and military officials, as well as official statements.

The watchdog documented what it said were 50 arbitrary arrests of residents, including 39 cases where the detainee was held incommunicado at an undisclosed location.

Some died in custody because of ill-treatment and lack of medical care, HRW said.

Reuters was unable to independently confirm its findings.

The report also documented 14 cases of extrajudicial killing of detainees, using methods that match similar cases reported in a Reuters investigation published in April.

A spokesman for Egypt’s State Information Service said he would not respond before seeing the report. A spokesman for the Interior Ministry had no immediate comment.

Conflict in the Sinai escalated after President Mohamed Mursi of the Muslim Brotherhood was toppled by the military in 2013.

Tens of thousands of North Sinai’s estimated 500,000 population have been forcibly evicted or fled while thousands have been arrested and hundreds secretly detained, HRW said.

The military spokesman said the razing of houses along Egypt’s border with Gaza was based on a cabinet decision issued in 2015 and that those affected had been compensated. A new town has been built with more than 10,000 housing units, he added.

The HRW report called on the United States, which gives $1.5 billion annually in aid, and Egypt’s other international partners to halt military and security assistance.

HRW also documented abuses by Sinai Province, the local branch of Islamic State, which it said has attacked civilians, kidnapping, torturing and beheading perceived opponents.

(The refiled story removes reference to the military in paragraph 11.)