The Taliban have captured Afghanistan's second biggest city of Kandahar, officials said on Friday, fueling fears the U.S.-backed government could fall to the insurgents as international forces complete their withdrawal after 20 years of war.

The Taliban also captured the towns of Lashkar Gah in the south and Qala-e-Naw in the northwest, security officers said.

The Taliban claimed to have captured the third-largest city of Herat in the west after days of clashes there but Reuters was unable to confirm that claim.