RAS AL AYN, Syria — Thousands of people fled Ras al Ayn Monday for the safety of Turkey as the battle between Syrian rebels and government troops for control of this border city raged for a fifth day.

Across the border in Ceylanpinar, Turkey, loudspeakers warned residents to stay indoors as Syrian jets and artillery raked rebel positions just a few hundred yards from Turkish territory, their shock waves shattering windows. At least one Syrian shell reportedly landed in Ceylanpinar.

Turkish soldiers watched from foxholes and tried to help the refugees, who crossed the border unimpeded except for some who became tangled in barbed wire. Most were ferried to a camp about 10 miles away by buses provided by the Turkish government, which made trip after trip throughout the day.

More than 100,000 Syrians are housed in refugee camps in Turkey, and thousands more have fled there without registering with the Turkish government. On Friday, more than 10,000 people reportedly fled to Lebanon, Jordan and Turkey — the highest single-day total of refugees since the conflict began. More than 8,000 of those fled to Ceylanpinar from Ras al Ayn.

A rebel spokesman in Ras al Ayn said it was possible that many or more fled Monday. Rebels said Syrian government airstrikes had killed at least 18 civilians, and it was unclear how many fighters died.

Residents of Ceylanpinar have opened their homes to the refugees, some of whom had tried to return to Syria before fighting prompted them to flee again.

“We have dozens of people staying in our house,” said 17-year-old Orhan Ahmed, who watched the fighting from the Turkish side of the border with friends. Despite the warnings to stay indoors, hundreds of residents were on the streets, watching the bombardment.

At least one airstrike hit a predominantly Kurdish neighborhood in Ras al Ayn, which has a sizable Kurdish minority. There were also reports of tensions between fighters and Kurdish militiamen loyal to the United Democratic Party, a Syrian Kurdish party that has close links to the Turkish Kurdish Worker’s Party.

The Turkish Kurd party has fought a decades-long war with the Turkish government seeking autonomy for millions of Kurds who live in southern Turkey. In the past few weeks, Syrian rebels and United Democratic Party militiamen have fought each other in northern Syria, including open fighting and tit-for-tat kidnappings in Aleppo, the country’s largest city.

Meanwhile, rumors swept rebel ranks that an attack was being planned on Hasaka, the largest city in this northeastern Syrian province of the same name, which has been largely free of rebel activity until the fighting at Ras al Ayn. Hasaka is Syria’s only majority-Kurdish province, and is an ethnic powder keg where tensions between the largely Arab rebels and the United Democratic Party are likely to get worse.

The rebel battalions fighting in Ras al Ayn include locals and outsiders. The main battalions appear to belong to a group that calls itself the Strangers of Damascus, and they say they belong to the Free Syrian Army, a group nominally led by defected military officers who live in a refugee camp in southern Turkey.