Cotabato City, Philippines  - Three people were injured when a bomb exploded in an amusement centre in a southern Philippine city, a regional military spokesman said Thursday.

Colonel Jonathan Ponce said the improvised explosive device went off late Wednesday inside the bathroom of the amusement centre in Cotabato City, 960 kilometres south of Manila.

Ponce said the attack was believed to be perpetrated by Moro Islamic Liberation Front (MILF) rebels in retaliation to ongoing military offensives against rogue MILF commanders who seized villages and attacked towns last August.

"We found out that it's part of the Muslim rebels' retaliatory attacks," he said. "They are now targeting civilians."

The blast was the second attack in Cotabato City in the week.

On Tuesday night, an improvised bomb tore through the Agong Lodging House in Cotabato City, injuring two people and destroying four rooms, Ponce said.

Authorities also blamed MILF rebels for Tuesday's attack.

But MILF spokesman Eid Kabalu denied that the rebel group had a hand in the attacks.

"It's purely speculation," he said. "They did not even conducted investigation and they are blaming it to us."

Peace talks between the MILF and the government have been stalled since August 2008 when the rebels launched deadly attacks to protest the non-signing of a key territory agreement that would have expanded an existing autonomous Muslim region.

More than 200 people were killed in the attacks and subsequent fighting with government troops, while more than 500,000 were displaced at the height of the conflict.

The 12,000-strong MILF rebels have been fighting for an independent Islamic state in the southern Philippine since 1978, but entered into peace negotiations with the government in 1997. (dpa)