A Japanese reporter has been killed after being caught in a gunfight in Aleppo, where fierce fighting continues to rage, according to Japan's foreign ministry.
Two other journalists who were travelling with Yamamoto are reportedly missing.
The death of 45-year-old Mika Yamamoto on Monday in the country's largest city takes to four the number of foreign journalists who have lost their lives since the uprising began in March 2011.
Japan's foreign ministry said Yamamoto had been working for the small Japan Press news agency, adding that a colleague travelling with her had identified the body.
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"She was doing reporting work in Aleppo, northern Syria, when she was caught in gunfire," an official said.
The US government-funded Al Hurra television station said Monday it had lost contact with two of its employees working in Syria - they were reportedly travelling with Yamamoto at the time of the attack.
Held by rebels
Correspondent Bashar Fahmi and his cameraman Cuneyt Unal had entered Syria early on Monday, according to Deirdre Kline, the director of communications for Middle East Broadcasting Networks, which operates Al Hurra.
"We have seen the YouTube video in which the Free Syrian Army states that Al Hurra correspondent Bashar Fahmi and his cameraman Cuneyt Unal were captured and detained in Aleppo, Syria," Kline said in a statement sent to the AFP news agency.
"We have not been able to get in touch with Mr Fahmi and Mr Unal since they entered Syria on Monday morning. We are currently working to gather more information about their status."
The video also showed the badly injured body of an Asian woman lying in what appears to be a hospital.
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A man who strongly resembles a picture on the Japan Press website of Kazutaka Sato, a colleague, bends over her body.
Sato told Japanese broadcaster TBS that Yamamoto had been shot in the neck.
The Britain-based Syrian Observatory for Human Rights (SOHR) said Yamamoto had died in Suleimanya, a district of Aleppo.
"She was seriously wounded Monday while covering the clashes at Suleimaniya which have been going on since yesterday. We took her to hospital where she succumbed to her injuries," Rami Abdel Rahman, the SOHR's head, told AFP news agency, citing medical officials from the hospital.
"She was very likely hit by a projectile."
Yamamoto was a known face on Japanese television who came to prominence after she survived air raids on the Palestine Hotel in Baghdad in 2003, in which two journalists from Reuters and a Spanish broadcaster were killed.
She joined Japan Press in 1995 and had also covered the war in Afghanistan and the Iraq conflict, according to the company's website.
The dead woman's father, retired journalist Koji Yamamoto, said reports of her death were "too much to bear".
"I can't believe it until I see her with my own eyes," the 77-year-old told Jiji Press by telephone.
"She was always talking about tragic people who were caught in conflicts, human lives and world peace. She was more than I was ... she is a wonderful reporter and daughter."
French reporter Gilles Jacquier was killed on January 11 at central Syria's Homs, where American journalist Marie Colvin and French photographer Remi Ochlik both perished on February 22.