GARDEZ, Afghanistan ? Terrified families huddled in basements or fled on foot Thursday as rival Afghan warlords waged artillery battles for control of this strategic town, killing at least 43 people and injuring dozens of others.

The fierce fighting gave new urgency to Afghan leader Hamid Karzai’s appeal for an expanded international security force to be deployed outside the capital, Kabul, to stave off such factional battles.

Laying siege to Gardez, the capital of strategic Paktia province, was Bacha Khan, a local warlord aligned with Karzai’s interim administration, which named him governor of the province. Local tribal elders refused to accept Khan’s appointment, so Khan moved to take the city by force.

The fighting could complicate American efforts including clandestine operations led by small bands of U.S. special forces to root out fugitive Taliban and al-Qaida fighters in Paktia province. Paktia, which borders Pakistan, includes numerous smuggling routes that Taliban and al-Qaida fugitives could use to escape Afghanistan.

Loud explosions, the dull thud of mortars and the rattle of heavy machine-gun fire echoed through the deserted streets of Gardez on Thursday as Khan’s troops, dug in atop a pair of hilltops south of the city, took aim at fighters loyal to the town’s tribal council, or shura, holed up in a fortress in the town center.

Karzai, who stopped in Britain en route home from a high-profile visit to the United States, met with Prime Minister Tony Blair and said there was overwhelming support among the Afghan people for a widening of the peacekeeping mission.

“It’s a demand of the Afghan people as a measure of commitment by the international community, as a symbol of their commitment to Afghanistan to stay on,” he said.

High-flying American warplanes circled overhead during Thursday’s fighting, but did not intervene, and a contingent of what local leaders said were U.S. special forces stayed out of sight at their base south of town.

Khan has been aiding U.S. special forces, and Karzai’s government which took power in December after the fall of the Taliban confirmed his appointment as governor, but only after Khan had laid claim to the post.

Rebuffed by the tribal elders, he moved Wednesday to try to take the town by force. His men pushed their way into the town, but were driven back by the shura’s fighters after a few hours. Stragglers were still being flushed out Thursday in house-to-house searches, shura commanders said.

Both sides claimed to have taken dozens of prisoners. Khan’s fighters acknowledged 10 dead and the shura forces 15; authorities said 18 civilians died in the two days of fighting. Dozens of others were injured.

There were scenes of suffering at Gardez’s rudimentary hospital, where mortar rounds fell close enough to shake the walls. Patients swathed in bloody bandages wailed in pain as doctors shook their heads and said they were out of painkillers and other basic supplies.

The hospital treated 28 wounded in the first 24 hours of fighting, and nine died, said Dr. Najib, the chief surgeon, who like many Afghans uses one name.

“The patients are afraid. We are close to the front lines, and they are hearing artillery and mortar fire,” he said. In a bed nearby, a little boy cowered, listening to the thunder of shellfire.

A corridor with puddles of blood on the floor served as a makeshift morgue. Eight bodies could be seen, covered in blankets.

Haji Saifullah, the Pashtun tribesman who heads the council, said Gardez would never allow Khan to take over as governor.

“No, no, no, we will never accept him!” said the white-bearded, turbaned Saifullah, interviewed at his mud-brick headquarters on Gardez’ northern edge. “He is a smuggler and a tyrant and a killer.”

Saifullah said the shura had sent the Afghan government a letter explaining their position and appealing that the appointment be rescinded.

Khan’s forces, though, said they would press ahead until the town’s defenses collapsed.

“We will take Gardez we will continue the fight,” vowed Jilani, a Khan aide who also uses only one name, in a satellite telephone call from the town of Khost, 30 miles to the southeast.

Gardez sits on barren high plains ringed by steep mountains, and for many frightened residents, there were few places to hide. A 35-year-old woman named Fariba said she fled with her six children moments before a mortar round struck.

“Now our house is destroyed. We ran away, we were very afraid,” she said, sheltering with her children at her sister’s house on Gardez’s northern outskirts.

An all-out conflict between Khan and the Gardez shura had been brewing for months. Khan accuses shura members of being Taliban and al-Qaida sympathizers, which they deny.

In December, Saifullah supporters accused Khan of calling in a U.S. airstrike on a convoy of Gardez shura members by wrongly identifying them as al-Qaida and former Taliban members. Twelve members of the convoy were killed.

Paktia province on the border with Pakistan has been a major target of U.S. military action since the Taliban fell.

A powerful Taliban commander, Jalaluddin Haqqani, held sway over much of the province, where he allowed al-Qaida to establish training camps and use cave and tunnel complexes. Those have been the target of repeated U.S. bombardment that continued into mid-January.

In other developments Thursday:

In Washington, Defense Secretary Donald H. Rumsfeld said the United States must prepare now for potential surprise attacks more deadly than those of Sept. 11. The United States launched its war on Afghanistan after its Taliban militia refused to surrender Osama bin Laden, chief suspect in the Sept. 11 terror attacks.

Another e-mail purportedly sent by the kidnappers of Wall Street Journal reporter Daniel Pearl extended the deadline for killing him by one day. Pearl was abducted last week while researching a story on Pakistan’s radical Islamic groups.

Afghanistan’s Ministry of Telecommunications reopened 18 neighborhood post offices in Kabul, which had been served by a single post office since the 1990s, Afghan television reported.