MANILA, Philippines — Philippine police have filed murder complaints against six Muslim militants from a little-known al-Qaida-inspired group they blamed for a bombing last month that killed eight people in a crowded bar in the south, officials said Wednesday.

Witnesses identified Usman Hapids of Khilafa Islamiyah Mindanao as the man who left a mortar round concealed in a bag that went off in a bar at a shopping mall complex, killing eight people and wounding 46 in Cagayan de Oro city, said regional police chief Catalino Rodriguez.

Rodriguez told a Senate committee that was looking into the July 26 blast that the complaints filed against Hapids and his companions before government prosecutors were part of a legal offensive to help discourage other such bloody attacks.

Despite a security alarm set off by the explosion, a series of bombings rocked other southern regions this week, including in Cotabato city, where a powerful bomb rigged into a small van exploded on a busy avenue during rush hour Monday, killing eight people and wounding more than 30.

Three bombs went off in the region on Wednesday, including a roadside explosive that wounded seven soldiers on board a passing army truck in Maguindanao province, near Cotabato city, regional military commander Maj. Gen. Romeo Gapuz said.

Another bomb that exploded Wednesday caused no injuries but damaged a bridge in Maguindanao's Datu Piang town.

Officials said that there was no evidence the bombings were connected and that different motives may be behind them, including terrorism and personal feuds.

"It hurts to say, but the impression given is that it's so easy for one to get attacked in the Philippines," Sen. Grace Poe-Llamanzares told top police officials in her law and order committee inquiry on the Cagayan de Oro bombing. "We should prevent this from happening."

Hapids was seen with five other suspected Muslim militants before he detonated the bomb in Cagayan de Oro, about 800 kilometers (500 miles) south of Manila, police senior inspector Pepito Reyes said in documents submitted to government prosecutors.

A government counterterrorism official said Hapids' group, Khilafa Islamiyah Mindanao, has fewer than 15 members and aspires to bring the southern Philippines under an Islamic caliphate, or religious state. Set up a few years ago, the group has staged a few bombings in the past, including at a hotel in Cagayan de Oro months ago, said the official, who spoke on condition of anonymity because he was not authorized to talk to reporters.

Another Muslim rebel group, the Bangsamoro Islamic Freedom Movement, claimed responsibility for the bomb attack Wednesday against the soldiers, who were returning to camp after buying supplies from a market in Shariff Saydona Mustapha town in Maguindanao province.

The group broke off from the Philippines' largest Muslim rebel group, the 11,000-strong Moro Islamic Liberation Front, two years ago. The breakaway guerrillas have rejected talks between the government and the main rebel group and have vowed to continue fighting for a southern homeland for minority Muslims in the predominantly Roman Catholic country.

Abu Misri Mammah, a spokesman of the rebel faction, said his group would continue attacks against government forces. Government troops have strengthened security in the south, concerned that the breakaway guerrillas may intensify attacks, including bombings when the holy Muslim month of Ramadan ends this week.