The Taliban assault on Helmand Province tests the resolve of the government at the start of talks to end the 19-year war, and could complicate President Donald Trump's pre-election pledge last week to bring home the remaining US troops by Christmas.
It is the first big Taliban offensive since talks between the government and the Taliban opened last month, and one of the biggest since the fighters committed to a ceasefire as part of a deal agreed with Washington in February to withdraw US troops.
The United States confirmed on Monday it had launched air strikes against Taliban fighters to push back the Helmand assault. US air strikes have been comparatively rare since February when Washington agreed to pull its troops out to end the longest war in US history.
Since Sunday, insurgents have seized military bases in Helmand and closed in on the provincial capital, Lashkar Gah.
The Helmand governor's media office said on Tuesday Afghan special forces, aided by air strikes from the country's air force, had managed to take back five checkpoints from Taliban control, killing 23 of the group's fighters.
Jets and helicopters continued to circle Lashkar Gah through the night on Monday and on Tuesday, attacking the Taliban's positions. The US military did not immediately say whether its forces or warplanes were involved.
Around 5,100 families have been displaced by the fighting, the head of the refugee and repatriation department, Sayed Mohammad Amin, said, adding that there was an urgent need for food and shelter.
Trump, lagging in the polls ahead of an election in three weeks, has long promised to withdraw US forces from Afghanistan. The Taliban welcomed his tweet last week that the troops should be "home by Christmas."
However, the withdrawal agreement requires the fighters to halt attacks on urban areas before US troops leave. In an interview with NPR on Sunday, Chairman of the Joint Chiefs of Staff General Mark Milley stressed that the withdrawal was conditions-based.
"We're monitoring all of those conditions closely. And we're, we the military, are giving our best military advice on those conditions so that the president can make an informed, deliberate, responsible decision."The talks between the government and Taliban in Qatar have moved slowly and are still in early stages. Both sides said on Monday that their contact groups had met.