|Video uploaded by activists showed the envoys attending the vigil for Matar
Several foreign ambassadors to Syria have travelled to the district of Daraya, near the capital Damascus, to attend a condolence ceremony for a prominent slain Syrian activist.
Footage posted by activists on YouTube of Tuesday's ceremony for Ghiyath Matar showed the ambassadors of the US, Japan and France seated among others in an apparent show of solidarity with the anti-government protest movement.
Matar, a leading figure in protests that challenge the Syrian Baath party's 41-year-long rule, was killed under torture by authorities, activists reported. His body was returned to his family on Wednesday, according to Human Rights Watch (HRW), the international rights group.
Hours after the visit by the envoys, government troops fired tear gas at the gathering of mourners, activists told the Associated Press news agency.
A spokesman for the Japanese embassy in Damascus told Al Jazeera that Toshiro Suzuki, the ambassador, had attended the ceremony to express condolences.
A US embassy official confirmed the visit of Robert Ford, the US ambassador visit, saying he was accompanied by other diplomats.
The attendances are likely to increase tensions between the countries represented by the ambassadors and Syria, which has imposed travel restrictions intended to prevent the diplomats from leaving the capital.
"The ambassador of the United States arrived in Daraya along with the French ambassador to offer condolences after the death of Ghiyath Matar," the rights activists were quoted by AFP as saying.
The visits came more than two months after Ford was condemned by the Syrian government for visiting the city of Hama in July in a show of solidarity for massive protests there.
Matar is just one of at least 95 Syrians who have died while in government custody since April, according to Amnesty International.
Also on Wednesday, Syrian troops conducted raids in the northwestern province of Idlib and the central region of Homs, the London-based Syrian Observatory for Human Rights said.
The Local Coordination Committees, an activist network, said one person was killed in Idlib and two others in the central province of Hama in Wednesday raids.
The violence came a day after more than 20 people were killed throughout Syria, according to the Observatory and Mustafa Osso, a Syria-based rights activist.
HRW also raised concerns about four other activists arrested last week near Damascus.
About 70,000 people have been arrested during the government's crackdown since protests erupted in March, and 15,000 dissidents remain in detention, according to the Observatory.
The United States on Sunday condemned Matar's killing.
"The United States condemns in the strongest possible terms the killing of Syrian human rights activist Ghiyath Matar while in the custody of Syrian Security Forces," Victoria Nuland, a US state department spokeswoman, said in a statement.
Nuland said Matar's "courage in the face of the Assad regime's brutal repression is well known in his home of Daraya and across Syria."
International pressure escalates
The United Nations says a total of 2,600 people, mostly civilians, have been killed during the government's crackdown. Opposition activists put the death toll at more than 3,000.
Syrian security forces have continued their campaign against anti-government protests despite mounting international pressure on Syrian President Bashar al-Assad's government to halt the crackdown.
In-depth coverage of escalating violence across Syria
Arab League foreign ministers on Tuesday issued a statement calling for an "immediate change... to stop the bloodshed", while Recep Tayyip Erdogan, Turkey's prime minister, said he feared the country was heading towards civil war.
Erdogan, who had previously described Assad as a personal friend, also distanced himself from the Syrian president.
"Nobody can be a friend with or trust an administration that fires bullets at its people and attacks its cities with tanks," Erdogan said. "A leader who kills his own people has lost his legitimacy."