"Ensuring the rule of law should become a top priority for the government of Afghanistan and its international friends - people are fed up," said Koenigs, who recently briefed members of the UN Security Council on the situation in Afghanistan.
In addition to an increasing number of insurgent attacks that, according to the UN, have killed more than 380 civilians in the past five months, Afghanistan's post-Taliban fragile political stability has been threatened by competing warlords who fear they will be marginalised during the country's transition to democracy.
On Sunday, five missiles were fired close to a location where Karzai was delivering a speech to a local gathering in the Andaar district of Ghazni province.
A government press release stated that no-one was hurt in the attacks.
"Those who did the attack do not value the millions of Afghans who voted for Karzai as their president - we utterly condemn it," Koenigs said.
The UN also denounced the recent assassinations of two female journalists in Kabul and Parwan provinces - both relatively free of Taliban insurgency.
Shakiba Saanga, an anchor for a TV station in Kabul, and Zakia Zaki, the director of a radio station in Parwan province, were both shot dead by unidentified armed men in separate attacks.
Lawlessness hinders progress
Lawlessness in Afghanistan is greatly hindering progress in the country. For the past five years, dozens of donor countries have spent billions of dollars on reconstruction and development in Afghanistan which, some Afghans say, have not brought tangible changes to people's daily lives.
Widespread insecurity in the south and south-east of the country has impeded rebuilding and development activities, donors and Afghan officials say.
The UN, too, is also not satisfied with the pace of development in Afghanistan, Koenigs told a briefing in Kabul on Monday.
According to him, some people, particularly in the south, have been alienated due to poor government performance and lack of development.
The UN has played a critical role in supporting post-Taliban arrangements in Afghanistan and garnering international assistance to help the country's transition to democracy and statehood.
Noor Akbari, an Afghan MP, told IRIN that the UN's plea for an end to lawlessness and a fresh start to development in Afghanistan is a clear warning to the national government and its international partners.
"I think the UN has realised the fact that Afghanistan has reached a crossroad of success and failure and that the international community should overhaul its security, reconstruction and development engagements in the country," said Akbari.