KABUL: The Taliban have captured Afghanistan's second biggest city of Kandahar, officials said on Friday, in the most significant setback for the US-backed government since the insurgents launched a new offensive as US forces withdraw.

"Following heavy clashes late last night the Taliban took control of Kandahar city," a local government official told Reuters after the militants announced they had taken it.

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Government forces were still in control of Kandahar's airport, which was the US military's second biggest base in Afghanistan during their 20-year mission.

Lashkar Gah captured

Separately, the Taliban also captured Afghanistan's Lashkar Gah, capital of the southern province of Helmand, after two weeks of heavy fighting, a police official said on Friday.

Government and senior armed forces officials flew by helicopter out of the government's last stronghold in the town at about midnight on Thursday, said the official, who declined to be identified.

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"About 200 ANDSF members, who were left in the governor's compound, with the intervention of elders, surrendered to the Taliban," said the official, referring to members of the national defence and security forces and tribal elders.