A bomb explosion at the weekend in Karen state that left four dead and over 30 injured was not the work of the rebel Karen National Union (KNU), its spokesperson has said.

The blast occurred during a pagoda festival at Ahnankwin village, outside the eastern state’s Kyarinnseikgyi township on Saturday night. Three people were killed on the spot and a 12-year-old girl died later at hospital.

“We are sad to hear it – it wasn’t the KNU’s work,” David Thackabaw said, suggesting the attack may be the work of groups “who want to disrupt” the KNU’s push for a ceasefire with the government.

Bomb attacks in Burma’s border regions are generally followed by accusations in state media that it was the work of an ethnic opposition army, although the government has so far remained quiet on Saturday’s incident.

The majority of the injured were sent to a hospital in the Mon state capital of Moulmein, the closest main town to where the attack took place.

A man from Ahnankwin village, which lies in territory controlled by the Burmese army, said the bomb “went off around the midnight with a large boom. I was there and consider myself extremely lucky to not have gotten hit.”

The KNU, whose armed wing the Karen National Liberation Army (KNLA) has been fighting the Burmese government for more than six decades, is due for another round of ceasefire talks with officials from Naypyidaw on Thursday this week.

It will be the fourth time the two sides have met since a new government came to power in March. Attempts to broker a truce have so far failed.