Three guards hired by NATO security forces were shot dead Thursday and the vehicle of an Indian road construction company was bombed, killing an Afghan worker, officials said. The attacks in eastern Afghanistan highlighted the weak security in a country struggling to cope with mounting insurgent and criminal violence seven years after the Taliban regime was removed in a US-led invasion. It was not clear who shot the three men working for NATO security forces in the eastern province of Khost, provincial government spokesman Kuchai Nasiri said. Similar attacks have been blamed on Taliban insurgents, who mostly target foreign and Afghan security forces and other people they perceive as allied with the government.