Nearly 200 people have been killed and more than 1,000 injured in the most recent wave of fighting in Libya, officials said this weekend.

The offensive to take control of Tripoli launched by Khalifa Haftar, a military commander based in the east of the country, is now in its second month.

There are increasing fears of a bloody stalemate that could claim the lives of many more civilians and fighters.

Haftar has urged his forces to “teach the enemy a greater and bigger lesson than the previous ones” during Ramadan, saying the holy month had not been a reason to halt previous battles in the eastern cities of Benghazi and Derna.

His comments came just hours after the United Nations called for a week-long humanitarian truce

Haftar’s offensive is aimed at toppling the UN-recognised Government of National Accord (GNA) in Tripoli and has the backing of Saudi Arabia and Egypt.

Last week, the World Health Organization (WHO) gave higher estimates of casualties that those given by the GNA’s ministry of health on Sunday, saying that 392 people have been killed and about 2,000 wounded in the ongoing armed clashes south of Tripoli.

“The number of displaced due to these clashes has risen to about 50,000 people distributed between Tripoli and other cities in the western region,” the WHO tweeted.

The US appears to have accepted the view of its chief Middle Eastern allies that Haftar’s assault can be seen as the act of a strong leader fighting Islamist extremist militias in Tripoli.

But many independent Libyan experts claim Haftar has no commitment to democracy, and himself deploys Salafist militia in his self-styled Libyan National Army.

At least nine people were killed in an attack on Saturday on a military training camp used by forces loyal to Haftar in the southern city of Sabha. The dawn assault was claimed by the Islamic State in a statement distributed through social media. The statement said it had targeted “Haftar’s heretical militia”.

The GNA said that Haftar was directly responsible for a resurgence in Islamic extremist activities in Libya.

“Ever since the offensive against Tripoli, we have warned the only beneficiaries … are the terrorist groups, and that what is happening will offer them a fertile ground to restart their activities,” it said.

Trump’s personal backing for Haftar appears to have undercut both the UN special envoy, Ghassan Salamé, and the UK Foreign Office’s efforts to secure a UN security council resolution calling for a ceasefire.

Both Russia and the US opposed British moves at the UN last month to pass a statement calling for a ceasefire and a return to talks.

The dramatic change in US policy followed a Trump meeting with Egyptian leader Abdel Fatah al-Sisi, and a phone conversation with the Abu Dhabi crown prince, Mohammed bin Zayed Al Nahyan. The two are Haftar’s principal backers.

The power struggle between Haftar, a former senior officer in the army of Muammar Gaddafi, and the GNA has left Libya’s vast desert regions without effective government.

Gaddaffi was deposed and killed in 2011.