By Mustafa Andalib and Storay Karimi
GHAZNI/HERAT, Afghanistan (Reuters) - Dozens of elite commandos were among the casualties suffered by Afghan security forces as the Taliban claimed to have taken a district in Ghazni province, stepping up battlefield pressure while seeking a political settlement with the United States.
Officials said about 25 Afghan commandos were killed in central Ghazni, where the Taliban have been battling militia from the mainly Shi'ite Hazara community in the districts of Malistan and Jaghori, a conflict coloured by hostility between ethnic Hazaras and Pashtuns.
U.S. forces were providing assistance, including intelligence and close air support, a spokeswoman from U.S. military headquarters in Kabul said.
Taliban spokesman Zabiullah Mujahid said Malistan had fallen but local security officials said fighting continued close to the district centre.
"Fresh troops have been sent to Malistan and Jaghori but the people are also cooperating and have stood up against the insurgents," Army General Chief of Staff, Mohammad Sharif Yaftali, told reporters.
Some commandos had been killed or wounded, he added, but gave no details. However security officials, speaking on condition of anonymity, said the commandos had been rushed in to unfamiliar territory and ambushed by Taliban fighters, many of whom now regularly use night vision equipment.
Afghanistan's highly regarded special forces units have suffered increasingly heavy casualties this year as the Taliban have mounted major assaults on provincial centres including Ghazni city and Farah city in the southwest.
At the same time as the Ghazni fighting on Sunday, about 50 police and soldiers were killed around Farah when Taliban fighters attacked checkposts in the city and nearby districts, regional officials said.
U.S. commanders have said they expect the Taliban to step up military efforts to better their position while they maintain contacts with U.S. special envoy Zalmay Khalilzad aimed at opening peace negotiations.
Khalilzad, an Afghan-born former U.S. ambassador to Kabul, met President Ashraf Ghani and other officials at the weekend, in his latest round of meetings following an initial meeting last month with Taliban officials in Qatar.
But Sunday's fighting underscores the pressure on Afghanistan's overstretched security forces, suffering from their highest level of casualties ever, estimates from the NATO-led Resolute Support mission show.
The government no longer releases exact casualty figures but officials say at least 500 men are being killed each month and hundreds more wounded, a tally many consider an underestimate.
The Ghazni fighting prompted demonstrations in Kabul and Ghazni by Hazaras, who have complained bitterly of official neglect after a string of attacks on their mosques and cultural centres. A suicide attack, close to where demonstrators had been gathering in Kabul, killed at least six people.
Taliban spokesman Zabiullah Mujahid denied fighters were targeting any particular ethnic group, reflecting concern that the fight in Ghazni was being interpreted as a sectarian issue.
The Taliban are a Sunni Muslim, mainly ethnic Pashtun movement but deny any sectarian agenda. However many Shi'ite Hazaras blame Pashtuns for the attacks against them.
Ghazni, briefly overrun by the Taliban in August, sits on the highway linking Kabul, the capital, to the major southern city of Kandahar. It is also a gateway into the mountainous central provinces of Hazarajat, home mainly to Hazara people.
Late on Sunday, Taliban fighters also attacked Farah city as well as checkpoints in the nearby districts of Khaki Safed and Bala Buluk, said Shah Mahmood Rahimi, deputy head of the Farah Provincial Council.
He said 45 Afghan police were killed in the fighting, along with five soldiers, but the militants had pulled back.
(Additional reporting by Mustafa Andalib in GHAZNI and Hamid Shalizi and Rupam Jain in KABUL; Writing by James Mackenzie; Editing by Clarence Fernandez)