Afghan and Taliban forces clashed again on the outskirts of Herat on Saturday, a day after a police guard was killed when a United Nations compound in the western city came under attack.

Violence has surged across the country since early May, when the militants launched a sweeping offensive as US-led foreign forces began a final withdrawal that is now almost complete.

The Taliban have seized scores of districts across Afghanistan, including in Herat province, where the group has also captured two border crossings adjoining Iran and Turkmenistan.

According to Afghan journalist Omid Sobhani, Taliban advanced toward the Herat city from the west side. They are now in Ghaibatan and Azad villages, just 5kms from the center of the city. Their security belt is in Ghaibatan village.

https://twitter.com/OmidSobhni/status/1421515770908102663

Officials and residents reported renewed fighting on the outskirts of Herat on Saturday, with hundreds fleeing their homes to seek shelter closer to the heart of the city.

Herat governor Abdul Saboor Qani said most of the fighting was in Injil and Guzara district -- where the airport is located.

"At the moment the fighting is ongoing in the south and southeast. We are moving cautiously and to avoid civilian casualties," Qani said.

Government forces also called an airstrike near a 10-bed hospital in Lashkar Gah, capital of Helmand province, that officials said had been seized earlier by the Taliban to treat its wounded fighters.

Residents told AFP that Taliban fighters took over the Ariana Afghan Speciality Hospital to treat those hurt.

"This morning, the Taliban fighters came and forced the hospital staff to leave," said Agha Mohammad.

"Planes were hovering in the air at that time, and they were following the Taliban, and the air strike happened."

Sher Ali Shakir, provincial public health director of Helmand, said the hospital was destroyed, one person killed, and two wounded.

Fighting hampers flood rescue

During fighting Friday, the main Herat compound of the United Nations Assistance Mission in Afghanistan came under attack from rocket-propelled grenades and gunfire that the UN blamed on anti-government elements.

The militants say they will not target foreign diplomats, but have blatantly violated international protocol before.

Abdullah Abdullah, former deputy president and now head of the High Council for National Reconciliation, tweeted Saturday that the Taliban had executed a senior Afghan army officer after capturing him near Herat.

"The Taliban, contrary to all the principles of war and Islamic and humanitarian standards, martyred Abdul Hamid Hamidi, commander of the 1st Brigade of the 207th Zafar Corps, after taking him captive," he said.

"Shooting prisoners of war is a cowardly act against all the rules of war and shows the cruelty of the Taliban."

In Herat, Afghan forces and militiamen of veteran warlord and anti-Taliban commander Ismail Khan have been deployed around the city of 600,000 in recent days.

Khan, who previously fought the Soviet occupation forces in the 1980s and then the Taliban during their hardline regime in the 1990s, has vowed to fight the insurgents again to counter their staggering advances in recent months.

Fighting was also hampering rescue efforts after severe flooding in Nuristan this week killed at least 113 people, with over 100 more missing.

"Unfortunately the area is under the control of the Taliban, we were unable to send our provincial teams to the area," said Tamim Azimi, spokesman for Afghanistan's state ministry for disaster management.

"But we have sent the (local) rescue teams along with the Afghan Red Crescent," he told AFP.