Haitian Prime Minister Garry Conille offered his surprise resignation on Friday after just four months in office, amid tension between the premier and government ministers over issues of dual nationality.

The resignation opens a new chapter in Haiti's political turmoil as it struggles to recover from the devastating 2010 earthquake.

Conille resigned after clashes over an investigation launched by lawmakers concerning foreign passports held by senior government officials, including President Michel Martelly. Haiti does not recognize dual nationality.

Martelly said in an address to the nation late Friday that he had accepted the resignation, but that he regretted the moving coming 'at a time when the country is taking off'.

Martelly vowed to 'rapidly' nominate a successor, and said he had assured 'our partners of the international community' that he had taken measures 'to allow the state to operate normally'.

Conille had publicly supported the lawmaker's investigation into the nationalities issue against the advice of his ministers, who lined up behind the president and refused to answer inquiries.

The investigation was launched by Senator Jean-Charles Moses, a fierce Martelly opponent who claims the president has US and Italian nationalities.

Disagreements over the probe led to a marked deterioration in relations within the administration, and Conille grew increasingly isolated in his position.

The move brings back political turmoil to Haiti as Martelly's administration struggles to ramp up stalled reconstruction efforts following the massive earthquake two years ago that leveled much of the capital Port-au-Prince.

In Haiti, the prime minister is appointed by the president and mainly serves as cabinet chief. Haiti's parliament approved Conille's appointment in October, temporarily ending months of political crisis.

He had been Martelly's third choice for prime minister since the president took office last May, but the first approved by parliament.

Conille had previously served as chief of staff in Haiti to former US president Bill Clinton, who serves as co-chair of the Interim Haiti Recovery Commission that oversees billions of dollars in post-quake aid to the country.

The US embassy in Haiti seemed unhappy with the move, and issued a statement urging the swift appointment of a new premier.

Washington 'has welcomed' Conille's 'effort, insight and energy' over the past four months, the statement read. 'We regret that Haiti will lose his service'.

The embassy urged Martelly and Parliament 'to work together swiftly to identify and confirm a new Prime Minister'.

"We continue to believe that political stability in Haiti is critical to its ability to attract the domestic and foreign investments needed to increase economic development and create jobs in Haiti," the statement read.

Officials with MINUSTAH, the UN stabilisation mission in Haiti, also seemed unhappy.

The head of the UN mission, Mariano Fernandez, expressed his 'deep concern' over the resignation, decrying that political divisions are being prioritised 'to the detriment of the country' while Haitians are waiting for developments 'which will lead towards reconstruction, economic growth and institutional strengthening of the rule of law'.

Canada also 'deeply regrets' Conille's resignation, Foreign Affairs Minister John Baird said in a statement, describing the ex-premier as 'a capable leader, a friend of Canada and a man who inspired a great deal of hope'.

Canada calls on Martelly and Haiti’s parliamentarians "to fulfill their responsibilities to the Haitian people and act expeditiously to install a successor," Baird said.

"Haitian leaders need to demonstrate a firm and unwavering commitment to democratic principles and the rule of law," he said.

The process of appointing a new prime minister and forming a government could take months, as Martelly does not have a majority in parliament.

Conille, a physician by trade, was educated in Haiti and received graduate training in health administration at the University of North Carolina at Chapel Hill as a Fulbright scholar.

He has also worked as the United Nations Development Program's resident representative for Niger.