"The people want the army restructured," they chanted in northern Sanaa. "The people want a new Yemen."

Similar protests took place in 17 other provinces, including Yemen's second-largest city Taez, witnesses said.

Yemenis have gathered every Friday for the past year to demand the ouster of former president Ali Abdullah Saleh who formally handed over power to Hadi on Monday, under a Gulf-brokered transition plan.

The power transfer deal stipulates that during a two-year interim period, Hadi will oversee a restructuring of the army.

On Friday, state news agency Saba said Hadi has named General Salem Ali Qatan to head the 31st Armoured Brigade in south Yemen, a post which General Mahdi Maqola, known for his close ties to Saleh and accused of corruption, had held for decades.

Hadi also appointed a new governor and new intelligence chief for the main southern city of Aden, a separatists' stronghold.

Anti-corruption strikes have spread across several military and government departments in the impoverished Arab country over the past two months.

Saleh had appointed relatives to head the country's military and security apparatus.

Air force soldiers have been staging protests calling for the ouster of their commander General Mohammed Saleh al-Ahmar, a half-brother of Saleh.

Saleh's son commands the elite Republican Guard troops while his nephew Yehya heads the central security services and Tariq, another nephew, controls the presidential guard.

The reforms were initiated in 2003 after liberalisation led to the introduction of medical fees and opened up disparities between city and countryside, leaving many with spiralling health costs and worsening care.

Publishing in The Lancet, Chinese statisticians led by Sarah Barber in the World Health Organisation's Beijing office looked at data from government-led surveys of hundreds of thousands of people in 2003, 2008 and 2011.

Over this period, insurance coverage increased from 29.7 to 95.7 percent of respondents, which meant about 1.28 billion people were covered in 2011, they found.

Physical access to health services was achieved to 83.3 percent of the population, a trend seen across geographical zones.

The average share of in-patient medical costs reimbursed from insurance also increased rapidly, from 14.4 percent in 2003 to 46.9 percent in 2011, although this meant that last year patients still had to pick up half of the tab.

Of greater concern, said the paper, was the high number -- 173 million -- of Chinese who faced "catastrophic" health expenses in 2011.

They amount to 12.9 percent of China's population, a proportion almost unchanged since 2003.

Such expense shocks are a major concern, because they "are very likely to contribute to poverty" by draining savings, said the study.

"As yet, the large public investments do not seem to have offered strong financial protection for households against catastrophic health events," it said.

The survey covered 193,000 people in 2003, 177,000 in 2008 and 59,000 in 2011.

The study's authors said the questionnaires have been used every five years since 1993 and described them as consistent and reliable barometers of health care.

But this was questioned by specialists with a US foundation, the China Medical Board (CMB), based in Cambridge, Massachusetts.

In a commentary also published by The Lancet, the CMB's Lincoln Chen and Dong Xu said "all sorts of biases" could arise in a survey whose questions were selected and then conducted by a government ministry.

"Given the growing maturation of health reform, China should consider establishing an independent commission consisting of stakeholders and academics," they said.