Iran's new ultraconservative President Ebrahim Raisi on Monday said that the "defeat" of the United States in Afghanistan must usher in a durable peace in the neighbouring, war-wracked country.

"The military defeat and the US withdrawal from Afghanistan should offer an opportunity to restore life, security and lasting peace in that country," Raisi said, quoted by his office.

The presidency statement came after the Taliban seized control of Kabul, but it did not mention the Taliban nor the fall of the Afghan capital.

Raisi, who made the remarks in a call with outgoing Iran's foreign minister Mohammad Javad Zarif, said the Islamic republic wanted good relations with Afghanistan.

Iran was "closely monitoring the evolution of events in Afghanistan" and wants good neighbourly ties with it, he said.

Raisi tasked Zarif and Iran's Supreme National Security Council to give him updated reports on the situation in Afghanistan, the statement added.

Iran shares a 900-kilometre (560-mile) border with Afghanistan, and hosts nearly 3.5 million Afghans, according to the UN refugee agency.

In 1998, Taliban troops entered the Iranian consulate in the northern Afghan city of Mazar-i-Sharif, killing several diplomats and an official news agency journalist.

The Taliban later said they had been killed by individuals acting independently, but Tehran held the movement responsible for the deaths, which sparked outrage and nearly triggered an Iranian military intervention in Afghanistan.

Analysts say Tehran is taking a pragmatic stance on the Taliban's resurgence in Afghanistan.

On Sunday the Iranian foreign ministry said it had reduced its diplomatic presence in Afghanistan.

The announcement came shortly after the Taliban reached the outskirts of the Aghan capital.

Foreign ministry spokesman Saeed Khatibzadeh said a skeleton staff remained at Iran's Kabul embassy and that employees had been also evacuated from three of out of five diplomatic missions in other Afghan cities.

Zarif meanwhile held Monday a meeting in Tehran with China's special envoy for Afghanistan Yue Xiaoyong, the foreign ministry said.

The talks focused on the situation in Afghanistan, it said.

Zarif on Sunday said that "Iran stands ready to continue its peacemaking efforts" in Afghanistan.

"Violence and war -- like occupation -- never solve problems," he wrote on Twitter.

His talks with the Chinese envoy come as a government spokeswoman in Beijing on Monday said China was ready to deepen "friendly and cooperative" ties with Afghanistan.