The United Nations says it is "deeply concerned" about the safety and protection of tens of thousands of people in Afghanistan's Lashkar Gah, who could be trapped by heavy fighting between Afghan government forces and the Taliban, a UN spokesman said.
The Taliban have stepped up their campaign to defeat the US-backed government since April as foreign forces complete their withdrawal after 20 years of war.
"Since the start of the year nearly 360,000 people have been forcibly displaced by the conflict in Afghanistan. About 5 million people have been displaced since 2012," UN spokesman Stephane Dujarric told reporters.
Fighting has been particularly heavy around the city of Herat, near the western border with Iran, and Lashkar Gah and Kandahar in the south.
"We're deeply concerned about the safety and protection of people in Lashkar Gah, in the south, where tens of thousands of people could be trapped by the fighting," Mr Dujarric said.
It comes as the Taliban said it carried out a bomb attack in Kabul targeting the defence minister, as the insurgents fought for control of a string of besieged cities across the country.
The bomb-and-gun attack on Minister Bismillah Mohammadi yesterday was one of the biggest in Kabul for months, bringing violence to the capital after intense fighting in the south and west of the country.
The Afghan and US militaries have carried out air strikes against the insurgents to push them back and the Taliban said the Kabul attack was a response to that.
"The attack is the beginning of the retaliatory operations against the circles and leaders of the Kabul administration who are ordering attacks and the bombing of different parts of the country," Taliban spokesman Zabihullah Mujahid said in a statement on social media.
It represents a major escalation by the Taliban, who have largely refrained from large-scale attacks in the capital in recent years after starting talks with the US on troop withdrawal.
The first bomb exploded in the centre of Kabul, sending a thick plume of smoke into the sky, AFP correspondents reported.
Less than two hours later, there was another loud blast followed by smaller explosions and rapid gunfire, also near the high-security Green Zone that houses several embassies, including the US mission.
The minister was safe and Afghan forces repelled the attackers, but at least eight people were killed, according to interior ministry spokesman Mirwais Stanikzai.
Mr Mohammadi later said it was a suicide car bomb attack targetting his house.
A security source said several attackers stormed a lawmaker's house after setting off the car bomb and shot at the residence of the minister from there.
Security forces had cordoned off the scene of the attack on Wednesday as troops inspected the buildings and cars damaged by the blasts.
Rubble covered the area while there were bloodstains on some of the floors.
"The Taliban justified this attack as the 'start of retaliatory attacks' against government personnel for their 'indiscriminate bombings'," Ibraheem Bahiss, a consultant with International Crisis Group, told AFP.
"However, it is equally possible that the Taliban has been caught off guard by the prevalence of anti-Taliban sentiments in Afghanistan's urban centres," he added.
The Taliban threat came after the Afghan military launched a counterattack against the insurgents in the southern city of Lashkar Gah.
The military had asked people to leave the city as they prepared for their offensive.
Resident Saleh Mohammad said hundreds of families had fled as fighting erupted between the two sides, trapping many in the crossfire.
"There is no way to escape from the area because the fighting is ongoing. There is no guarantee that we will not be killed on the way," Mohammad said.
"The government and the Taliban are destroying us."
The insurgents have taken control of vast swathes of the countryside and key border towns, taking advantage of the security vacuum left by the withdrawal of US forces.
The Taliban are now targeting cities, with fierce fighting for a week around Herat near the western border with Iran, as well as Lashkar Gah and Kandahar in the south.
"Those families which had financial support or a car have left their homes. The families who can not afford to are obliged to stay in their own homes as we are," resident Halim Karimi told AFP.
"We don't know where to go or how to leave. We are born to die."
The loss of Lashkar Gah, the capital of southern Helmand province, would be a massive strategic and psychological blow for the government.
Meanwhile, Human Rights Watch accused the Taliban of "summarily" executing detained soldiers, police and civilians with alleged ties to the Afghan government in areas they had recently seized.
The rights group said it had also obtained a list of 44 people who were killed by the Taliban in the town of Spin Boldak, which the insurgents captured last month along the border with Pakistan.
"Taliban commanders with oversight over such atrocities are also responsible for war crimes," Patricia Gossman, associate Asia director at HRW said in a statement.
Washington and London have also accused the insurgents of committing atrocities that may amount to "war crimes" in Spin Boldak.
