WASHINGTON — Escalating its assistance to Kurdish fighters battling the Islamic State in the Syrian town of Kobani, American military aircraft on Sunday dropped ammunition, small arms and medical supplies to resupply the combatants, officials said.

The United States and its Arab allies have conducted more than 135 airstrikes in and around Kobani in the past two weeks to help slow the advance of hundreds of Islamic State fighters on the town along the Turkish border.

But in a sign of the growing symbolic and operational significance of the town to both sides, three United States C-130 transport planes for the first time dropped 27 bundles of supplies provided by Iraqi Kurdish authorities to help the Syrian Kurds continue to resist the militant attempts to seize it, American officials said late Sunday.