Story highlights NEW: UN secretary-general issues condemnation of attack

The Taliban claimed to have been targeting intelligence staff members

Kabul, Afghanistan (CNN) The Taliban have claimed responsibility for a car bombing in Kabul that left at least 31 people dead, as the Islamist fundamentalist group ratchets up an offensive across Afghanistan.

The blast happened at around 6:40 a.m. Monday (10:10 p.m. ET Sunday) when a Toyota Corolla exploded in the city's west, Afghan Interior Ministry spokesman Najib Danish told CNN.

It is the latest in a string of attacks in recent days by the Taliban, which said it had captured two districts in northern and central Afghanistan at the weekend.

An Afghan security official inspects the scene of the bombing on Monday.

In a statement released by Taliban spokesman Zabiullah Mujahid, the group said the Kabul bomb's target was a bus carrying Afghan intelligence staff, but Danish said that all the victims were civilians, including some employees of the Ministry of Mining and Petroleum. Women and children were among the dozens injured, Danish said.

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