DOHA/baghdad - Islamic State militants have closed gates of a dam on the Euphrates River in western Iraq, reducing the water and giving them greater freedom of movement to attack government forces downstream on the southern bank, local officials said.

The militants have redirected the flow of water to their advantage on the battlefield around the city of Ramadi. But the tactic also threatens southern provinces with drought and the water has been reduced to worrying levels, the officials said. The Euphrates has acted as a barrier between the militants who control its northern bank and pro-government forces who are are trying to advance towards Ramadi on the other side.

A spokesman for the governor of Anbar province, of which Ramadi is the capital, said security forces would now have to redeploy along the river to prevent the insurgents from infiltrating. “Previously they had to monitor only the bridges and certain areas, but now all of the river will be crossable,” Hikmat Suleiman said.

Islamic State has previously sought to use water as a weapon in its war against the Iraqi government. Last summer, the militants seized the Mosul dam in northern Iraq and threatened to submerge Baghdad until Kurdish forces drove them back with the help of airstrikes from an international coalition. The Anbar provincial council met on Wednesday to discuss how to respond. One member, Taha Abdul Ghani, suggested the government should bomb one of the dam’s gates to release the water.

Residents of Ramadi and a local irrigation official said however the insurgents had left two of the dam’s gates open, apparently to avoid flooding areas under their own control upstream. The partial closure of the Ramadi dam has forced more water into a tributary running south to the Habbaniya lake, officials said. Falih al-Essawi, a senior provincial security official, said the government had opened another dam to channel water from the Habbaniya Lake back into the Euphrates and prevent shortages in the southern provinces. But he said this was only a temporary measure that would not be effective for more than three days. “The government must act immediately otherwise dire consequences and an environmental catastrophe will be inevitable,” he said.  Moreover, the Islamic State group is a “global threat” which will take a generation or more to defeat, Washington’s envoy for the US-led coalition fighting the militants said Wednesday.

Despite “strategic momentum” against IS - or Daesh as he called it - General John Allen conceded that the fight would continue for several years in a keynote speech to the US-Islamic World Forum in Doha, Qatar. And he added that if IS was not defeated it could “wreak havoc on the progress of humanity”.

“This will be a long campaign,” he said. “Defeating Daesh’s ideology will likely take a generation or more. But we can and we must rise to this challenge.

“In an age when we are more interconnected that at any other time in human history, Daesh is a global threat.” In a wide-ranging speech, Allen added that IS also poses a new type of threat because of its “depravity”. “As someone who has spent nearly four decades as a United States marine, I have come closer than many to the reality of inhumanity.  “But I have never seen before the kinds of depravity and brutality in this region that ISIL represents and, in fact, that ISIL celebrates,” he added, using an alternative acronym for IS.

Allen was speaking the day after attending talks in Paris with ministers from around 20 coalition countries. The meeting followed the fall of the city of Ramadi, the capital of Iraq’s largest province Anbar, to IS. That loss has been described as the worst defeat for the coalition since it formed nearly a year ago.

Meanwhile, US deputy secretary of state Antony Blinken said on Wednesday that more than 10,000 militants have been killed in air strikes against the Islamic State group over a nine-month coalition campaign.

“We have seen enormous losses from Daesh (IS), more than 10,000 since the beginning of the campaign and this will end up having an impact,” Blinken told French radio, without specifying whether the losses were in Iraq or Syria. Blinken was speaking a day after an international conference in Paris in which 20 or so representatives of the anti-IS coalition pledged support for Baghdad’s plan to claw back territory from the marauding militants who have conquered large parts of Iraq and Syria. The coalition’s strategy has been criticised for relying on air strikes without committing boots on the ground, but Blinken stressed there had been “significant progress”.

Islamic State now controls “25 percent less of Iraq after nine months, a lot of their equipment has been destroyed and many Daesh members have been eliminated,” said Blinken.

He nevertheless acknowledged the “resilience” of the group after the coalition has launched about 4,000 air strikes on them.

In a separate French radio interview, Iraq’s ambassador to France, Fareed Yasseen, said the allies had heeded Baghdad’s calls for more weapons to combat the group.

“The Americans have promised us and will shortly deliver missiles that will make the difference against these truck bombs ... which made us lose Ramadi,” a key Iraqi city close to the capital.

“The French will be giving us similar weapons, ammunition and we are discussing other cooperation projects,” the ambassador told Europe 1 radio.