President Bashar al-Assad of Syria has insisted he has no information on James Foley and Domenico Quirico, two journalists missing inside the war-torn country.

"At present we have no information about the two journalists you mentioned," Assad said in an interview with Argentinian news agency Telam and daily Clarin.

A transcript of the interview was published by Syrian state news agency SANA.

During the interview, according to Clarin, Assad was asked specifically about the fate of Foley, a US citizen and AFP contributor, and Quirico, a veteran reporter for Italian daily La Stampa.

But the SANA transcript made no mention of the reporters' names, transcribing the question as asking about a reporter of "Italian nationality" and another who "was reported missing after he entered six months ago".

"There have been certain cases where journalists have illegally entered Syria without the knowledge of the Syrian government," Assad said, according to the SANA transcript.

"They entered into areas that have a known presence of terrorists and according to their media organisations have gone missing.

"We continue to search for them through our on-going military operations, and on occasions our forces have been successful in releasing journalists who were kidnapped in areas infiltrated by terrorists.

"Whenever there is information regarding journalists who have entered Syria illegally, we directly communicate with the concerned country," Assad insisted.

Foley, 39, is a freelancer who worked for AFP, GlobalPost and other outlets and is believed to have been seized by armed men in northern Syria's Idlib province on November 22.

On May 3, his family said there were indications he was being held at by military intelligence unit at a detention centre near Damascus.

Quirico has not been heard from since April 9, after he entered Syria from Lebanon three days earlier.

The 62-year-old journalist has long experience in conflict zones, having covered stories in Libya, Sudan and Mali.

The Syrian government has issued limited visas to journalists and tightly restricted where they can go and what they can cover.

The restrictions have prompted reporters to make increasingly perilous journeys into Syria across its borders with Turkey and Lebanon.

Assad was also asked about the fate of two Syrian bishops who were kidnapped in the north of the country on April 22.

"We have preliminary information that they are near the Turkish-Syrian border," he said.

"We are closely following this issue and liaising with the Orthodox Patriarchate in Syria to free them from the terrorist groups who abducted them."

Bishop Yohanna Ibrahim, head of the Syriac Orthodox Church in Aleppo, and Bishop Boulos Yaziji, head of the Greek Orthodox church in Aleppo went missing in Aleppo province.