The drive will cover Jhenidah, Kushtia, Chuadanga, Meherpur, Jessore, Khulna, Satkhira, Bagerhat and adjacent districts that virtually bristle with outlaws and see frequent bloodshed, a senior police official said.

Locals allege that the groups indulge in robbery, killing, extortion, rape and other criminal activities in the name of erasing their enemies.

"All regular defensive measures and combing operations by police have miserably failed to bring the situation under control," he said.

"The government has decided the more intense and serious move looking back on past drives."

About 15,000 additional police, ansar and Bangladesh Rifles (BDR) personnel will be sent to the region from relatively peaceful areas, he added.

Under the drive, area-wise raids will be conducted amid a virtual curfew to maximise the chances of outlaws' arrest.

The country's porous borders that largely run through plains and along small rivers will be plugged during the drive, the official said.

Three main underground parties -- Purbo Banglar Communist Party (PBCP), Biplobi Communist Party-Haq Group (BCP) and New Biplobi Communist Party -- are locked in perennial armed struggles in the region.

The decades old turf war between arch-rivals PBCP and BCP, believers in extermination of class enemy, has gathered pace recently.

Sources say some of the leaders of the BCP are blessed by a section of the ruling alliance.

"The majority of the BCP outlaws are now going untouched in the on-going police raids," said a top police official.

"It is enshrining the PBCP belief that police are on the side of the class enemies and they should be eliminated as well."

Police believe such a mindset triggered a spate of attacks on the law-enforcers in Khulna, Sirajganj and some other areas in recent months.

A number of policemen were killed and their arms and ammunition looted in the attacks.

Traditionally, the outlaws were largely armed with 303 rifles, double-barrel guns and in some cases with stenguns, smuggled into Bangladesh by gunrunners from India.

But now the outlaws are equipping themselves with sophisticated modern weapons including AK-47 and other types of assault rifles, available in Chittagong and the Chittagong Hill Tracts region.

The gaining of strength by the PBCP and BCP as well as other underground parties has posed a serious threat to peace in the southwestern region.

Prime Minister Khaleda Zia at a rally in Bagerhat on Saturday hinted a joint drive, without specifying the timeframe.

Extreme left politics trickled into the southwestern region from eastern Indian state of West Bengal where the ideology thrived in 1960s.