Mullah Abdul Ghani Brader, a senior Taliban military commander, has been captured in Karachi, Pakistan's largest city, US media has reported.

According to The New York Times, Mullah Brader, the Afghan Taliban's number two, was captured in a secret raid by US and Pakistani intelligence forces several days ago.

Citing US government officials, the newspaper said Mullah Brader had been in Pakistani custody for several days and was being interrogated by US and Pakistani agents.

The New York Times described him as the most significant Taliban figure captured since the start of the Afghanistan war.

However, a Taliban spokesman denied the report of his capture, saying he was still in Afghanistan actively organising the group's military and political activities.   

"He has not been captured. They want to spread this rumour just to divert the attention of people from their defeats in Marjah and confuse the public," Zabihullah Mujahid told Reuters, referring to a US-led Nato offensive in Afghanistan's Helmand province.