Abuja - Nigeria's ruling party on Sunday called on the country's people to support efforts by President Muhammadu Buhari to recover billions of dollars lost to government corruption and punish the perpetrators in the graft-plagued nation."The level of looting that went on... is better imagined, hence the need for all Nigerians to rally around the Buhari administration to recover the [money], bring the looters to justice and to put in place measures to prevent such looting in the future," the All Progressives Congress (APC) said in a statement. The Nigerian National Petroleum Corporation (NNPC), which manages the nation's multi-billion dollar oil industry, is widely considered to be one of the most corrupt state agencies and Buhari has launched a probe into its activities.Since taking office in May after being elected on an anti-graft ticket, Buhari has dismissed his entire military brass and sacked key officials of the country's giant NNPC oil firm in a bid to clamp down on graft.The APC said part of the stolen or unaccounted money included about €18bn out of €36bn earned from crude oil between 2012-2015 that was withheld by NNPC and $2.1bn from the excess crude account - money to be kept aside for a rainy day. It also said $15m from a botched arms deal with South Africa was yet to be returned to Nigeria while $13bn in dividends from the exports from Nigeria of liquefied gas remains unaccounted for.The party condemned calls on Buhari from some quarters to be lenient on those responsible for the corruption. "Anyone who attempts, either by deeds or words, to sabotage the recovery efforts is not a patriot and deserves nothing but public opprobrium," it said. A failure to go after those engaged in graft is tantamount to "offering a thumbs-up for looting. No responsible government will do that," the APC said. Buhari has slammed the state of the country's finances, claiming his predecessor had left Africa's biggest economy deep in debt and the treasury "virtually empty". The president appointed a new head of NNPC earlier this month just after sacking the entire board. Nigeria is Africa's largest oil producer, churning out roughly two billion barrels of crude per day. Ordinary people have largely not benefited from the nation's oil wealth, however, with much of the revenue lost to graft.