(Adds wounded security officials, details)
By Saud Mehsud
DERA ISMAIL KHAN, Pakistan, Nov 25 (Reuters) - A bomb killed at least four people and wounded about 70 near a Shi'ite procession in Pakistan on Sunday, police said, as the sect braced for major sectarian attacks by Sunni militants during a critical event in their religious calendar.
Television footage showed the wounded being carried away in the northwestern city of Dera Ismail Khan, where a bomb targeting Shi'ites killed at least seven people, including four children, on Saturday.
"Four bodies have been shipped here and more than three dozen are wounded. The death toll will likely rise because many of the injuries are serious," said Khalid Aziz Baloch, a doctor at a district hospital.
The bomb, planted in a shop beside a street market, also wounded five security officials, said senior police official Malik Mushtaq.
Hardline sectarian Sunni groups, which are becoming increasingly dangerous, have threatened more attacks as the Shi'ite morning month of Muharram comes to a climax on Sunday.
Security officials say organisations such as Lashkar-e-Jhangvi (LeJ) are stepping up attacks on Shi'ites, who they regard as non-believers, in a bid to destabilise nuclear-armed, U.S. ally Pakistan and establish a Sunni theocracy.
Al Qaeda, which is close to LeJ, pushed Iraq to the brink of a sectarian civil war several years ago with large-scale suicide bombings of Shi'ites.
More than 300 Shi'ites have been killed in Pakistan so far this year in sectarian conflict, according to human rights groups. The campaign is gathering pace in rural as well as urban areas such as Karachi, Pakistan's biggest city.
Shi'ites account for up to 20 percent of this nation of 180 million.
Washington, a critical source of financial aid for cash-strapped Pakistan, has been pressuring the South Asian nation to crack down on militants based in tribal areas who cross the border to attack American-led forces in Afghanistan.
Pakistan, meanwhile, faces major domestic security challenges from a wide range of groups, including the Taliban, who capitalise on issues such as unemployment, official corruption and poverty to recruit people.
(Additional reporting by Jibran Ahmad in PESHAWAR; Wrtiting by Randy Fabi; Editing by Michael Georgy and Nick Macfie)