American freelance journalist Austin Tice, who has been unaccounted for in Syria for more than two weeks, has been captured and is being held in Syrian government custody, according to people familiar with the matter, including a senior diplomat.

Tice, 31, contributed stories to The Washington Post, McClatchy Newspapers and other publications this summer after crossing into Syria in May. His reports offered glimpses into conditions on the ground in areas where the fighting was fast intensifying.

The Georgetown law school student and former U.S. Marine Corps infantry officerhas not been heard from since mid-August, when he told friends and family members that he intended to leave Syria.

In an appearance on a Czech television station on Monday, Czech ambassador to Syria Eva Filipi said of Tice that “our sources report that he is alive and that he was detained by government forces on the outskirts of Damascus, where the rebels were fighting government troops.”

The Czech Embassy has been responsible for U.S. interests in Syria since the U.S. Embassy was shuttered in February amid security concerns. Filipi said her staff would continue to seek information about Tice’s whereabouts and welfare in the coming days.

Her account has subsequently been corroborated by others who are familiar with Tice’s whereabouts, and who said he had been detained near the Damascus suburb of Darayya.

The Syrian government has not responded to official inquiries about Tice, according to the U.S. State Department. A Syrian official in Washington declined to comment on Friday on the Czech ambassador’s remarks.

Tice’s family on Thursday called for him to be released, as did The Post and McClatchy.

“Austin is our precious son, and we beseech the Syrian government to treat him well and return him safely to us as soon as possible,” Tice’s parents, Marc and Debra, said in a statement.

“We’re investigating reports that Austin Tice is in the custody of Syrian authorities,” Marcus Brauchli, The Post’s executive editor, said in a statement. “If the reports are true, we urge these authorities to release him promptly, unharmed. Journalists should never be detained for doing their work, even — and especially — in difficult circumstances.”

Anders Gyllenhaal, McClatchy’s vice president for news, said Tice “is a widely respected and dedicated journalist. If he is in fact being held by the Syrian government, we would expect that he is being well cared for and that he will be quickly released.”

As fighting between troops loyal to Syrian President Bashar al-Assad and rebel fighters has intensified in recent months, reporting in Syria has become increasingly perilous. Tice entered the country at the Turkish border. He and many other journalists have used that route because the Syrian government issues few visas for journalists who wish to cover the conflict.

Ten journalists have been killed since the uprising in Syria began in the spring of 2011, including five foreigners, according to the advocacy organization Reporters Without Borders. At least 30 Syrian citizen journalists have also died since the start of the conflict. More than 17,000 people — most of them civilians — have died in the Syrian civil war, according to the United Nations.

Two journalists with Al-Hurra TV — Palestinian reporter Bashar Fahmi and his Turkish cameraman Cuneyt Unal — went missing on Aug. 20 in Aleppo. Unal recently appeared on a pro-Syrian government television channel, apparently under coercion.

Reporters Without Borders on Thursday called for Tice’s prompt release and demanded that all journalists who have been detained or kidnapped be freed immediately.

A number of other foreigners, including at least one additional American, have been held in Syrian custody, according to people familiar with the matter in Damascus and outside of Syria who asked not to be identified because of the sensitivity of the topic.

The names of the detained individuals have not been released, and it could not be determined if they remain in Syrian captivity.

The State Department said Thursday that it would continue to work through the Czech government to obtain information about Tice’s welfare and whereabouts.

Joel Simon, the executive director of the Committee to Protect Journalists, said that “all sides in Syria must ensure the safety of media personnel and respect their internationally recognized status as civilians.”