A bomb struck a convoy of road construction workers heading to their site in eastern Afghanistan early on Wednesday, wounding an Indian engineer and three Afghans, police said.
The blast -- similar to scores blamed on extremists behind a bloody insurgency in Afghanistan -- hit the vehicles after they left the southeastern city of Khost, the police chief of Mando Zayi district told AFP.
"They were on their way to their work site when their vehicles were struck by an explosion and three people, including a foreign engineer -- an Indian engineer -- were wounded," said the official, Mohammad Jamal.
It was not clear if the blast was a landmine or remote-controlled bomb, Jamal said. Two vehicles were damaged in the explosion, he said.
The Indian government runs several important reconstruction projects in Afghanistan as part of international efforts to help the country rebuild after nearly three decades of war.
The group hit in Wednesday's blast were working on a road between Khost and the neighbouring town of Gardez.
President Hamid Karzai last month opened a 217-kilometre (134-mile) road built by India through southern Afghanistan to the border with Iran that is intended to give the landlocked country access to Iranian ports.
The road was regularly attacked by Taliban insurgents.
Indian Foreign Minister Pranab Mukherjee said at the opening ceremony that six Indians and more than 100 Afghans lost their lives building the road, according to a statement released by the Afghan government at the time.