Afghan Interior ministry spokesman Yousif Stanikzai said the driver was released on Monday and is being questioned by local intelligence agents.

The four men were kidnapped on Saturday in southwestern Nimroz province by suspected Taliban rebels.

They were working for an Indian company refurbishing the main road from the southern city of Kandahar to Herat in the west.

In the capital Kabul overnight, Stanikzai said militants fired three rockets, destroying a house but causing no casualties.