Donors at a conference on Afghanistan have pledged to give it $16bn (£10.3bn) in civilian aid over four years, in an attempt to safeguard its future after foreign forces leave in 2014. The biggest donors, the US, Japan, Germany and the UK, led the way at the Tokyo meeting in offering funds. The pledge came as Afghanistan agreed to new conditions to deal with endemic corruption. There are fears Afghanistan may relapse into chaos after the Nato pullout. The Afghan economy relies heavily on international development and military assistance. The World Bank says aid makes up more than 95% of Afghanistan's GDP. Meanwhile in Afghanistan itself two roadside bombs killed 14 civilians and injured another three in the southern Kandahar province, regional police chief Gen Abdul Raziq said. The first bomb hit a car, and the second exploded when a tractor arrived to rescue the wounded. Women and children are among the dead, the regional governor's office said. 'Fragile' In his opening remarks at the conference, Afghan President Hamid Karzai pledged to "fight corruption with strong resolve". He said that despite the progress made in the past 10 years, Afghanistan's economy remained vulnerable and security a major obstacle. "It will take many years of hard work on our part as Afghans, as well as continued empowering support from our international partners before Afghanistan can achieve prosperity and self-reliance," he said. "We must do what we can to deepen the roots of security and make the transition irreversible." UN Secretary-General Ban Ki-moon echoed Mr Karzai's remarks, saying progress in Afghanistan remained "fragile". "Failure to invest in governance, justice, human rights, employment and social development could negate investment and sacrifices that have been made over the last 10 years," said Mr Ban. US Secretary of State Hillary Clinton stressed the need for reform to safeguard changes achieved in Afghanistan. "That must include fighting corruption, improving governance, strengthening the rule of law, increasing access to economic opportunity for all Afghans, especially for women," she said. The Tokyo conference is being attended by high-level delegates from more than 70 nations and international organisations. Participants had promised $4bn in annual aid between 2012 and 2015, Japanese and US officials said, in return for mechanisms to monitor the Afghan government's progress on improving governance and combating endemic corruption. Military support The civilian aid sought in Tokyo comes on top of $4.1bn in military assistance for Afghanistan's armed forces pledged by a summit of Nato leaders in Chicago in May. According to plans endorsed at the Chicago meeting, Nato-led forces will hand over combat command to Afghan forces by mid-2013, followed by a withdrawal of combat troops by the end of 2014. After that, only training units will remain. Speaking during a brief stop-over in Kabul on her way to Tokyo on Saturday, Mrs Clinton announced that the US had given Kabul the status of "major non-Nato ally". The a move is seen as another signal aimed at allaying Afghan fears about waning Western support. The designation as major non-Nato ally, which already includes close US allies such as Australia and Israel, gives Kabul easier access to advanced US military technology and streamlines defence co-operation between the countries. The last country to be granted the status was Pakistan in 2004. In May, US President Barack Obama and his Afghan counterpart, Hamid Karzai, signed a 10-year strategic partnership agreement outlining military and civil ties between the countries after 2014.