Violence has surged across Afghanistan despite the presence of almost 150,000 foreign troops, with military and civilian death tolls reaching record levels.

The NATO-led International Security Assistance Force (ISAF) said three of its service members had been killed in two roadside bomb attacks in the south on Thursday and Friday.

There was no immediate explanation for the attack late on August 19 in the Sangin district of Helmand province in which the road crew workers and security guards were killed, although construction crews are frequently targeted.

"A group of Taliban attacked the site with machine guns and rockets, killing 25 of my workers," said an official from the Afghan Construction company who identified himself as Aqa January

Mohammad Mamaluddin, the Helmand deputy police chief, said the death toll had later risen to 30 and that another 17 were wounded.

He said the attackers had also set fire to machinery and taken about 12 four-wheel drive vehicles.

Reuters