Suicide attackers on Tuesday targeted NATO troops in Kabul and a police headquarters in restive southern Afghanistan, killing three people and wounding at least 60 as the Taliban’s bloody summer offensive showed no signs of letting up.A powerful blast echoed around the Afghan capital as a suicide car bomber hit a NATO military convoy on the main road to the airport, around 500 metres (550 yards) from the US embassy, killing at least one Afghan civilian and wounding around 20.