Hundreds of Syrian refugees poured into a Turkish-Syrian border crossing Saturday, fleeing intense fighting between Syrian Kurds and militants from the Islamic State group in nearby towns and villages.

The mass displacement of Syrians came as Kurdish fighters announced they are making headway toward Tal Abyad, a stronghold of the extremist group near the Turkish border. The Kurds are backed by U.S.-led coalition airstrikes that have added to the fears of the fleeing civilians.

Some 13,000 refugees have already crossed into Turkey in the last 10 days, according to the Turkish Foreign Ministry. Hundreds more could be seen Saturday on the Syrian side of the Akcakale border crossing, waiting to cross into Turkey.

A statement by the main Syrian Kurdish fighting force, known as the YPG, said its fighters have laid siege to the Islamic State-held town of Suluk, a few miles southwest of Tal Abyad. It said IS militants have "lost control" over Suluk and Kurdish forces were advancing toward Tal Abyad.

The loss of Tal Abyad would be a major blow to the IS group.

The border town is a major avenue for commerce for the extremist group -- through which it smuggles in foreign fighters and sells black-market oil. The city is also a key link between Turkey and the northern Syrian city of Raqqa, the de-facto capital of the Islamic State group's self-declared caliphate.

In Syria, a country now split mostly between Islamic militants and forces loyal to President Bashar Assad, the U.S. has found a reliable partner in the country's strongest Kurdish militia, the YPG. They are moderate, mostly secular fighters, driven by revolutionary fervor and deep conviction in their cause.

Since the beginning of May, they have wrested back more than 200 Kurdish and Christian towns in northeastern Syria, as well as strategic mountains seized earlier by the IS group. Along the way, they have picked up ammunition, weapons and vehicles left behind by the jihadis.

The Islamic State group still holds about a third of Iraq and Syria, including Iraq's second-largest city, Mosul. ISIS fighters continues to battle Iraqi security forces and Shiite militiamen for territory north and east of the capital, Baghdad.

In Iraq, coordinated Islamic State suicide attacks targeting Iraqi government security posts killed 13 people Saturday north of Baghdad, as security forces repelled more suicide attacks by the extremists in Anbar province, authorities said.

Four suicide bombers driving explosive-laden cars rammed into two security checkpoints and a military headquarters in the al-Hajaj area within a 15-minute span, killing 13 Shiite militiamen and troops and wounding 24, police said.

Al-Hajaj lies on the road between Beiji and Tikrit in Salahuddin province. The key refinery town of Beiji has been the scene of fierce fighting between Islamic State militants and government troops, backed by Shiite militias, who took control of the town's center a few days ago.

Meanwhile, police said security forces repelled Islamic State suicide attacks near the town of Garma, east of militant-held city of Fallujah. The attackers used four suicide cars in the assault that left no casualties among the government forces, they said. Recently received U.S. anti-tank missiles were used to destroy the suicide cars, police and military officials there said.

Hospital officials confirmed the casualty figures from the Salahuddin province attacks. All officials spoke on condition of anonymity as they weren't authorized to speak to journalists.

Iraqi forces, backed by Shiite militias and U.S.-led airstrikes, have been struggling to regain control of the vast areas lost to the Islamic State group during its stunning blitz last year.