Government forces have launched operations against the Taliban in 18 provinces of Afghanistan as fighting has intensified since the start of the insurgents' spring offensive this month, the ministry of defense said on Saturday. The operations, backed by air power and artillery have been concentrated in areas where the Taliban insurgents have been aggressively challenging government forces seeking to reassert control over key districts. Eighty anti-government fighters, including nine from Islamic State have been killed over the past 24 hours in the east, while six soldiers have been killed, a defense ministry statement said.. The Taliban, which has ruled out joining peace talks while foreign troops remain in Afghanistan, announced the start of its spring offensive on April 12, pledging large-scale attacks against government strongholds as well as suicide bombings and targeted assassinations. Army chief of staff Qadam Shah Shaheem told reporters the Taliban was conducting "psychological warfare" designed to weaken morale and undermine confidence in the government but that it would not succeed. Frustrated by a stalled peace process and by the Taliban's growing attacks, President Ashraf Ghani has instructed the government forces to go on the offensive, security officials say. Speaking in parliament this week, Ghani branded the Taliban terrorists and vowed to avenge the killings of Afghans, in a marked escalation of government rhetoric against the insurgents. Government forces have beaten off a Taliban offensive in the northern city of Kunduz, which fell briefly to the insurgents last year, and appear to have stabilized the situation in the southern province of Helmand, where they pulled back from several districts in February. However heavy fighting has continued sporadically in both regions and government and NATO officials say they expect more tough fighting after a difficult year in 2015 when around 5,500 soldiers and police were killed. In one of the biggest single attacks in Kabul since 2011, a Taliban truck bomb killed at least 64 people and wounded hundreds more on April 19. The insurgency has gained strength since the withdrawal of international troops from combat at the end of 2014, with the Taliban stronger now than any point since they were driven from power by US-backed forces in late 2001.