A suicide-bomb and gun attack in Kabul’s Green Zone that targeted Afghanistan’s acting defence minister and killed eight people on Tuesday was claimed by the Taliban, as the hardline Islamist group continued to escalate violence across the country.

The suicide bombing, which targeted the house used by Bismillah Mohammadi, was one of the most significant in the Afghan capital in recent months. It came amid heavy fighting in the south and west of the country as the Taliban have sought to take three key cities.

The attack took place in the wealthy Sherpur neighbourhood, located in a section of the capital known as the Green Zone, where security is tight.

In a statement claiming responsibility, the Taliban spokesperson, Zabihullah Mujahid, said: “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.”

Mujahid said the attack was made in revenge for recent attacks by Afghan national forces in various provinces that he said caused civilian casualties and displacement. At least four Taliban fighters were killed in the assault.

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 United States on troop withdrawal.

The attack came amid reports that at least 18 civilians, including women and children, had been killed by an airstrike in the southern city of Kandahar as a further 49,000 people were displaced by fighting in the country.

The Kabul attack came in two parts. A first bomb exploded in the centre of Kabul, sending a thick plume of smoke into the sky. It was followed by a second blast around two hours later, then by smaller explosions and rapid gunfire, also near the high-security Green Zone that houses several embassies, including the US mission.

Afghan forces repelled the attackers, leaving the minister unharmed, but at least eight people were killed.

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.

The Taliban threat to Kabul came after the Afghan military launched a counterattack against the insurgents in the southern city of Lashkar Gah, the capital of Helmand province, which the Taliban has swept through, capturing most of the city’s districts.

The military asked people to leave the city on Tuesday as they prepared an offensive.

Saleh Mohammad, a resident, said hundreds of families had fled as fighting erupted, 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.”

An Afghan military spokesperson said an emergency had been declared in Lashkar Gah and government forces were getting reinforcements and US air support. “Special forces have been sent to the area. They are in good morale,” Gen Ajmal Omar Shinwari told Reuters.

The loss of Lashkar Gah would be a huge blow for the government, which has pledged to defend strategic centres after losing many rural districts to the Taliban in recent months.