| PESHAWAR, Pakistan
PESHAWAR, Pakistan A gunman working as a guard killed a rival of Pakistani Taliban leader Baitullah Mehsud on Tuesday, security officials said, dealing a blow to a government plan to defeat al Qaeda ally Mehsud.
The murder came as the military prepares an offensive against Mehsud, who has been accused of a string of bomb attacks including the assassination of former prime minister Benazir Bhutto in 2007.
Separately, U.S. drone aircraft struck twice in a Mehsud stronghold in South Waziristan near the Afghan border, killing six fighters in the morning, and then attacking the funeral of one of them and killing four more, intelligence officials said.
The murdered militant commander, known as Qari Zainuddin, had recently spoken out strongly against Mehsud and may have been about to mount a challenge against him. He was killed in the northwestern town of Dera Ismail Khan, police said.
"I confirm that Qari Zainuddin has been shot dead," Salahuddin, superintendent of police in the town, told Reuters.
The gunman was a guard for Zainuddin, an intelligence official said. He wounded another man and escaped.
Militants in northwest Pakistan are split into several factions, some of which are rivals.
The military went on the offensive against Taliban fighters allied with Mehsud in the Swat valley, northwest of Islamabad, in May and are in the final phase of that operation, the army says.
The offensive in Swat came after Taliban gains raised fears for the future of nuclear-armed Pakistan, a vital ally for the United States as it strives to defeat al Qaeda and stabilize Afghanistan.
The government has also ordered an offensive against Mehsud in his South Waziristan stronghold near the Afghan border.
In recent days, the military has been launching air strikes on Mehsud's bases while soldiers have been securing the main road into the mountainous region populated by ethnic Pashtun tribes.
The first drone strike on Tuesday was aimed at freshly built Taliban bunkers, said a resident of the area, Mohammad Daud.
In the second attack, one or more drones fired three missiles at a funeral of one of those killed in the morning, killing four people and wounding three, intelligence officials said.
The United States has carried out about 42 drone strikes since the beginning of last year, most since September, killing more than 345 people, including many foreign militants, according to reports from security agents, officials and residents.
Also on Tuesday, Pakistani aircraft attacked a compound in South Waziristan where a large number of militants were gathered for a meeting, intelligence officials said. There was no immediate word on casualties.
The United States has offered a reward of $5 million for information leading to Mehsud's location or arrest.
Zainuddin's strong statements against Mehsud in recent days had led to speculation authorities were encouraging him to stand up to his rival.
Suspicion for his murder has fallen on Mehsud, who was accused of being behind the killing of a prominent anti-Taliban cleric in a suicide bomb attack in the city of Lahore this month.
A security analyst said Zainuddin's killing was a setback for government efforts against Mehsud but authorities should not depend on Mehsud's rivals to get rid of him.
"He is al Qaeda number one in Pakistan," said Mahmood Shah, a former security chief in the Federally Administered Tribal Areas (FATA) in Pakistan's northwest. "This chap is too strong and a strong strategy is needed to deal with him."
Zainuddin was from the Mehsud tribe and would have had much useful information for the security forces about the workings of the Taliban, said veteran journalist Ismail Khan.
"That would have been very handy, he was a Mehsud (tribe) insider," Khan told Dawn Television.
In the southern city of Karachi, police said they had arrested five of Mehsud's men involved in bank robberies and kidnappings committed to raise money for the Taliban.
The fighting in Swat sparked an exodus of hundreds of thousands of civilians. Aid workers now fear a flow of villagers out of South Waziristan when fighting intensifies there.
Nearly 2 million people have fled fighting in the northwest, most since the army pushed into Swat in May, and another 40,000 or more have fled from South Waziristan even before the offensive there begins.
The United Nations is appealing for $543 million in aid to avert a long-term humanitarian crisis but has received only 35 percent of that.
Pakistan is being kept afloat by a $7.6 billion International Monetary Fund loan, underscoring the need for outside help for the displaced.
(Additional reporting by Zeeshan Haider, Faisal Aziz and Hafiz Wazir; Writing by Robert Birsel; Editing Paul Tait)