By Aung Hla Tun and Jared Ferrie
YANGON (Reuters) - Several bombs exploded in northeastern Myanmar on Thursday, police said, the latest in a string of unexplained attacks, including a blast this week that injured an American tourist in a plush hotel in the country's commercial capital.
Investigations are proceeding into the motive behind the string of bombings that have killed at least two people and wounded four over five days in four different regions. Myanmar's two biggest cities, Yangon and Mandalay, have both been hit.
The latest explosions struck Namkham, a town in Shan state bordering China, where ethnic rebels have been battling government forces.
"I don't know if there's any connection between these latest blasts and the incidents in Yangon and Mandalay," a police official in the capital, Naypyitaw, told Reuters on condition of anonymity as he was not authorized to speak to media.
Local media said the Namkham blasts had killed one person and injured two, including a child. Reuters was not able to verify the information.
The government says the bombings seek to alarm the public and raise doubts in the international community that Myanmar, formerly known as Burma, can guarantee security when it takes the rotating chair next year of the Association of South East Asian Nations (ASEAN).
They add to sporadic outbreaks of violence in a year that has seen euphoria over democratic reforms launched by President Thein Sein give way to sectarian attacks in different regions.
In the most prominent attack, an American woman was hurt when a bomb went off late on Monday, apparently in a bathroom, in the 22-storey Traders Hotel in Yangon.
The U.S. embassy condemned the attacks on Thursday, saying they "had no place in civilized society".
Police said four suspects had been arrested over bombings in Yangon, Mandalay and a third city, Sagaing, 20 km (12 miles) outside Mandalay.
But a man believed to have been behind an explosion in Tuangoo, 55 km (33 miles) outside the capital Naypyitaw, was still at large. That bombing killed two people.
"They confessed to carrying out these things because they were paid," said the senior police officer, referring to the arrested suspects.
He gave no further explanation and asked that his name be withheld as he was not authorized to speak to journalists.
A senior police officer in Mandalay said information provided by those detained over the Yangon incidents had led to the arrest of a suspect in Mandalay, where an unexploded device was found in a restaurant. Another suspect was at large.
The same men were accused of setting off a bomb in a car park and planting a device in a Buddhist pagoda, both in Sagaing.
"We were able to identify them from the CCTV footage of the pagoda and the restaurants," the officer said.
Myanmar is no stranger to bombings, but they have been rare since Thein Sein's reformist government took power in 2011 after an election that ended 49 years of military rule.
Three explosions during a Burmese New Year festival in 2010 killed at least 10 people. In 2005, three bombs at a convention center and markets killed 23, an attack blamed on ethnic minority rebels and an exiled political group.
(Editing by Martin Petty and Ron Popeski)