The Turkish government should investigate hundreds of alleged killings and other rights abuses in Turkey's southeast, the UN human rights office has said, releasing a report on an upsurge in violence there over 18 months.

Based on “remote monitoring”, the report says that around 2,000 people, including 1,200 local residents and 800 security forces, were reportedly killed during the security sweep between July 2015 and December 2016.

The crackdown comes as Turkey has faced many destabilising factors in recent years, including deadly extremist attacks, a failed coup and an influx of refugees from Syria. Meanwhile, Kurdish fighters – some allegedly linked to the Kurdistan Workers' Party (PKK) rebel group – have been making inroads in a fight against the Isis group in Syria.

The 25-page report, which draws on confidential accounts, satellite imagery and other sources, cites the destruction of nearly 1,800 buildings and the reported displacement of at least 355,000 people during the security sweep.

It seeks investigations so that “perpetrators of unlawful killings are brought to justice”, an end to “unannounced, open-ended, 24-hour curfews” and “reparations for victims and family members” whose rights have been abused.

UN human rights investigators have failed to gain access to the largely ethnic Kurdish areas of the south-east despite nearly a year of attempts to do so. Rights office spokesman Rupert Colville said the Ankara government “hasn't really given reasons” why access hasn't been granted.

Mr Colville said the investigation could be domestic, but it would need to be “seen as independent and impartial”.

In pictures: Turkey coup attempt Show all 17 1 /17 In pictures: Turkey coup attempt In pictures: Turkey coup attempt Turkish President Erdogan attends the funeral service for victims of the thwarted coup in Istanbul at Fatih mosque on July 17, 2016 in Istanbul, Turkey Burak Kara/Getty Images In pictures: Turkey coup attempt Soldiers involved in the coup attempt surrender on Bosphorus bridge with their hands raised in Istanbul on 16 July, 2016 Gokhan Tan/Getty In pictures: Turkey coup attempt A civilian beats a soldier after troops involved in the coup surrendered on the Bosphorus Bridge in Istanbul, Turkey, 16 July, 2016 REUTERS/Murad Sezer In pictures: Turkey coup attempt Surrendered Turkish soldiers who were involved in the coup are beaten by a civilian Reuters In pictures: Turkey coup attempt Soliders involved in the coup attempt surrender on Bosphorus bridge Getty In pictures: Turkey coup attempt Supporters of Turkish President Recep Tayyip Erdogan wave flags as they capture a Turkish Army vehicle Getty In pictures: Turkey coup attempt People pose near a tank after troops involved in the coup surrendered on the Bosphorus Bridge in Istanbul, Turkey, 16 July, 2016 Reuters In pictures: Turkey coup attempt Turkish soldiers block Istanbul's Bosphorus Brigde Getty In pictures: Turkey coup attempt A Turkish military stands guard near the Taksim Square in Istanbul Reuters In pictures: Turkey coup attempt Pierre Crom/Twitter In pictures: Turkey coup attempt Turkish soldiers secure the area as supporters of Recep Tayyip Erdogan protest in Istanbul's Taksim square AP In pictures: Turkey coup attempt People demonstrate in front of the Republic Monument at the Taksim Square in Istanbul Murad Sezer/Reuters In pictures: Turkey coup attempt Turkish soldiers detain police officers during a security shutdown of the Bosphorus Bridge Reuters In pictures: Turkey coup attempt Turkish Army armoured personnel carriers in the main streets of Istanbul Getty In pictures: Turkey coup attempt Chaos reigned in Istanbul as tanks drove through the streets EPA/TOLGA BOZOGLU In pictures: Turkey coup attempt Turkish President Tayyip Erdogan speaks to media in the resort town of Marmaris Reuters In pictures: Turkey coup attempt Supporters of President Erdogan celebrate in Ankara following the suppression of the attempted coup Reuters

He said UN human rights chief Zeid Ra'ad al-Hussein was “alarmed by the apparent significant deterioration” in human rights in Turkey, “which he believes is only serving to deepen tensions and make longer-term instability more likely”.

“It appears that not a single suspect was apprehended, and not a single individual was prosecuted, for violations that occurred during this period” from July 2015 to August last year, Mr Colville said.

Turkey's government has “contested the veracity” of some allegations in the report, Mr Colville said, without elaborating. Turkey's foreign ministry didn't immediately respond to a request seeking comment.

The rights office said Turkey's government had indicated that the PKK, which Ankara, the European Union and others consider a terror group, had attacked and killed some security forces.

The report cites “complex challenges” that Turkey has faced since the failed coup in July, but added that measures in a subsequent state of emergency “appear to have largely targeted dissent in general and political parties of the opposition in particular” – especially people of Kurdish origin.

It cited accounts from witnesses and family members of victims in the town of Cizre who “painted an apocalyptic picture of the wholesale destruction of neighborhoods”.