Kabul (dpa) - A district in southern Afghanistan's Helmand province fell to the Taliban on Wednesday, an official said, amid a day of fighting that undermined calls from the president for an end to insurgent violence.

"Today at 2 pm (0930 GMT) our security forces have tactically retreated from Khanishin district center, after three days of heavy clashes, resulting in the death of 16 Afghan security personnel," Mahmood Ashna, a spokesperson for Helmand police, said.

The police chief of Khanishin district was wounded in the clashes with the Taliban, Ashna said, adding that Afghan security forces are on the outskirts of the district centre preparing to retake the territory.

"We have prepared for the counter attack and also sent Afghan Special Forces to the area," he said.

Meanwhile, Afghan President Ashraf Ghani said in Islamabad on Wednesday that he was ready to seek peace with groups which shun violence, amid hopes of renewed talks with Taliban insurgents.

"Violence is not the way in a democratic society," the Afghan leader said on opening the Heart of Asia conference with Pakistan Prime Minister Nawaz Sharif.

"I strongly reiterate our commitment to lasting and just peace with all movements," he said, adding that the offer only stands to groups who lay down their arms and participate in a democratic process.

Delegates from over 30 countries and 12 organization attended the conference. They urged "all Afghan Taliban groups and all other armed opposition groups to enter into peace talks with the Afghan Government" in a closing joint declaration.

But their appeals were undermined as Taliban and Afghan forces continued a 24-hour battle at the airport in Helmand's neighbouring Kandahar province, resulting in scores of casualties.

The Kandahar airport siege began Tuesday evening and has left at least 35 people dead, most of them civilians, an official said on Wednesday.

"Among the dead are women, children and army soldiers," Defence Ministry spokesman Dawlat Waziri said.

"Nine attackers are killed, one still resisting the security forces, and 35 civilians are wounded."

A nascent peace process between Afghanistan and the Taliban launched in Pakistan in July was put on hold after the announcement of the death of Mullah Omar, the former Taliban chief.

Recent reports that the current leader, Mullah Akhtar Mansoor, was shot have thrown more uncertainty onto this latest attempt to revive talks.

Dozens of deaths were reported Wednesday from intense fighting between rival Taliban factions in the west of the country, according to government officials.

The two armed groups loyal to either Manssor or Mullah Rasul are fighting due to the recent spilt in the Taliban movement, since the announcement of Taliban founder Mullah Muhammad Omar's death this year.

"In the last 48 hours of battle, between rival Taliban commanders in Shindand district, we have reports of more than 100 people killed and 27 others wounded from both sides," Herat provincial police spokesman Abdul Rauf Ahmadi said.

Prisoners have reportedly been taken by both sides.

Ahmadi said both factions have called for reinforcements to continue the fighting. The battle began in the village of Zerko, and many families have been forced to flee the area. No civilian casualties have been reported.

An official told dpa that Ghani and Sharif agreed to restart the talks with the Taliban on the sidelines of the Heart of Asia summit. "The exact timing of the talks will be decided by officials of the two sides," he said.

Pakistan is considered to have influence over the insurgents and can play role in setting the talks.

Earlier, Ghani told the delegates in his opening address that Afghan security forces were learning fast and 2016 will be far better in term of security. He also thanks the international community to help his country face security threats.