Gunmen launch major attack on Pakistani prison holding militants DERA ISMAIL KHAN, Pakistan (Reuters) - Grenade-wielding Taliban fighters battled Pakistani security forces during a sophisticated midnight attack on a major prison holding hundreds of Taliban and other militants, police said on Monday. Fighting continued into the early hours of Tuesday, and security forces said they had imposed a curfew on the city, Dera Ismail Khan, 200 miles west of Lahore. The Pakistani Taliban sent 100 fighters and seven suicide bombers on a mission to free some of their top leaders, said Taliban spokesman Shahidullah Shahid. He said they had freed around 300 prisoners, a claim that could not immediately be verified. Some of the suicide bombers had blown up at the prison walls and some were in reserve, he said. The prison houses around 5,000 prisoners. Around 250 are Pakistani Taliban and members of banned sectarian groups such as Lashkar-e-Jhangvi, a Sunni militant group that has killed hundreds of Shi'ite civilians this year. Up to 40 gunmen wearing police uniforms launched their attack by blowing up the electricity line to the prison and detonating heavy explosions that breached the outer walls, said provincial prisons chief Khalid Abbas. It's completely dark in there. We don't know what's going on but there is fighting," he said. The militants fought their way inside using rocket-propelled grenades and machine guns, district police chief Sohail Khalid said. Mushtaq Jadoon, the town's civil commissioner, said dozens of prisoners had escaped. "The Taliban have loudspeakers and they are calling the names of their friends," he said. The gunmen also took over a nearby house and hospital, holding the residents hostage as they fired on police from the rooftops and laid ambushes for reinforcements. Police Constable Gul Mohammed said he was rushing to the scene when he was challenged by two young boys holding rifles. They told me to stop. I told them I am a policeman, and that's when they opened fire," he said, adding that he was shot three times. Police said there were other small groups of gunmen in the streets leading to the prison. The number of casualties was unclear because the fighting was ongoing. Police said they had called for military reinforcements. Provincial authorities received warning of the impending attack two weeks ago, said one security official in the provincial capital of Peshawar. He said phone intercepts indicated the militants were planning a jail break and interrogations of captured fighters confirmed it. Security officials alerted the provincial governor of the threat based on the intercepts. The attack raises questions over how well-prepared Pakistani security forces are after a series of high-profile attacks. Last week, militants stormed the headquarters of the Pakistani military intelligence service in the southern town of Sukkur. Over the weekend, around 40 people were killed in twin bombings in mainly Shi'ite areas in the town of Parachinar. Pakistani militants have launched successful raids on prisons several times before. Last year, nearly 400 prisoners were freed when the Taliban attacked a prison in the northern town of Bannu. After that attack, militants told Reuters they were helped by insiders in the security services. An inquiry later found there were far fewer guards on duty than there should have been and those who were there lacked sufficient ammunition. The attack comes the day before Pakistan's lawmakers are due to choose a president and two days before a major Shi'ite festival, which security officials have warned could be attacked. The front-runner for Tuesday's election to the largely ceremonial position is a close ally of Prime Minister Nawaz Sharif, whose party swept national elections in May and who has promised to seek talks with militant groups. An analysis by Reuters found that militant violence had sharply increased since Sharif took power. Additional reporting by Jibran Ahmad in Peshawar; Writing by Katharine Houreld; Editing by Robin Pomeroy and Philip Barbara