Tanzanian authorities have launched a national audit to find "ghost workers" and remove them from civil service payrolls under a corruption crackdown ordered by the president, a minister said.

The public sector wage bill has escalated sharply over the past few years, analysts say, partly because of the numbers of people registering fake names to collect extra wages.

A 2015 audit found the government had paid 141.4 billion shillings ($64.80 million) to fake workers over that year.

"We are conducting an audit of employees across the entire civil service to establish the scale of the problem and cut ghost workers from the payroll," Angellah Kairuki, Tanzania's minister for public service management told Reuters.

Businesses have long said corruption and government inefficiency were major obstacles to investing in Tanzania, which ranked 117 out of 168 countries in Transparency International's 2015 index of least corrupt countries. No. 1 is deemed the least corrupt.

Tanzanian President John Magufuli promised to focus on fighting corruption after taking office in November. Last week he threatened to sack cabinet ministers who do not declare their assets or failed to sign an integrity pledge.

He has already dismissed several senior officials, including the head of the government's anti-graft body, the chief taxman, a senior rail official and the head of the country's port authority.

Last month, the government spent 573.7 billion Tanzanian shillings ($263 million) to pay the salaries of 556,418 civil servants - equivalent to more than half the government revenues taken in over the same period.