BEIRUT (Reuters) - A Lebanese military prosecutor ordered forensics to examine the bodies of four Syrians who died in army custody last week following calls for an inquiry by rights groups, a judge said on Saturday.

The four, who the army said had died due to chronic illness, were among several hundred people arrested in a raid at Syrian refugee camps in the Arsal area of northeastern Lebanon.

The Lebanese Center for Human Rights said torture had led to the deaths of at least four detainees. The Syrian National Coalition -- a Turkey-based opposition group -- said 10 people had died in custody, some as the result of torture, and 19 others had died in the raid around Arsal town.

A military source denied the allegations, which prompted Lebanon’s human rights minister to call for an investigation into the deaths this week.

New York-based Human Rights Watch also demanded an independent probe, saying anyone responsible for wrongdoing should be held to account.

Judge Dany Zeeny said on Saturday three doctors appointed by military prosecutor, Judge Sakr Sakr, had taken samples from the bodies on Friday to a medical laboratory in Beirut.

The army said five suicide attackers blew themselves up while attacking soldiers during last week’s raid, killing one civilian.

Lebanon’s military has received hundreds of millions in military assistance from the United States and Britain in recent years, as part of efforts to bolster Lebanon against a threat from militants across the Syrian border.

The Lebanese army says it regularly stages operations targeting Islamic State and former al Qaeda-linked militants in the mountainous border region near Arsal.

A U.S. State Department official said Washington was committed to helping the army “secure Lebanon’s borders... and maintain overall security.”

“We have seen reports of Syrians who recently died while in custody of the Lebanese army and look forward to an official investigation into these deaths,” the official added.

More than one million registered refugees fleeing the six-year Syrian war have poured into Lebanon, a quarter of its population, according to the U.N. refugee agency. The number is widely put at closer to 1.5 million refugees.