* New leader won first elections since 2009 coup
* Explosion kills one, injures dozens after inauguration
By Alain Iloniaina
ANTANANARIVO, Jan 25 (Reuters) - Madagascar's new president Hery Rajaonarimampianina, who won the first elections since a coup in 2009, took office on Saturday but his inauguration was marred by an explosion that killed one person and wounded dozens after the ceremony.
The government said initial investigations showed the blast was caused by a grenade that was thrown near Mahamasina stadium where a musical show was taking place in the evening, hours after the inauguration there.
"The new president had just been sworn in. We know the political situation. His inauguration may not have pleased everyone. That's perhaps one of the reasons why this happened," said Arsene Rakotondrazaka, minister of internal security, who was at the scene.
He said a child aged 12 was killed and 33 people were wounded, seven of them critically. Extra police were deployed afterwards in several parts of the capital.
Rajaonarimampianina had earlier pledged to create an investment-friendly climate in the Indian Ocean island.
The World Bank said on Friday the next step of forming a government was crucial and that a resumption of normal lending hinged on the appointment of a new prime minister.
CLIMATE FOR INVESTMENT
"We need to put in place the structures ... that lead to development. We need to put in place a climate for investment that respects the rule of law," Rajaonarimampianina said as he took office.
The former finance minister won the presidential election on Dec. 20, the first in the country since the 2009 coup that plunged Madagascar into a political crisis that has sharply slowed economic growth and deepened poverty.
Outgoing president and former coup leader Andry Rajoelina, who backed Rajaonarimampianina in the vote, has said he may seek the prime minister's post in the new government.
Rajoelina, and the man he ousted in the coup, Marc Ravalomanana, were barred from standing in the presidential elections under the terms of a deal brokered by regional African states meant to end the political turmoil.
Jean Louis Robinson, who was defeated by Rajaonarimampianina, pledged on Saturday to organise and unite the island state's fractured opposition.
Full results of the parliamentary elections held alongside the second round of the presidential vote have not been released.
Rajoelina said his MAPAR coalition had won about 50 of the assembly's 151 seats. If confirmed, that would give it the biggest bloc and allow MAPAR to nominate the premier.
The World Bank expects the economy of the nickel-producing state to grow by 3.7 percent this year, accelerating to 4 percent in 2015.