BEIRUT - U.N. observers have discovered 13 bound corpses in eastern Syria, many of them apparently shot execution-style, the monitoring mission said Wednesday.
The announcement comes days after a massacre in Houla, in the central Homs province, which killed more than 100 people and prompted worldwide condemnation against the regime of President Bashar Assad. The Syrian government denied its troops were behind the killings and blamed "armed terrorists."
The latest killings apparently happened in Deir el-Zour province. The corpses were found with their hands tied behind their backs, according to a statement by the U.N. mission. Some appeared to have been shot in the head from a short distance.
The head of the U.N. observer team, Maj. Gen. Robert Mood, said he was "deeply disturbed by this appalling and inexcusable act."
The violence in Syria is spiraling out of control as an uprising against Assad that began in March 2011 has morphed into an armed insurgency.
In the wake of the Houla massacre, the United States and several other countries expelled Syrian diplomats to protest the killings. Survivors blamed pro-regime gunmen for at least some of the carnage in Houla.
The U.N.'s top human rights body planned to hold a special session Friday to address the massacre.
The U.S. Treasury Department also said it was levying sanctions on a key Syrian bank as it seeks to ratchet up economic pressure on the regime. The department said the Syria International Islamic Bank has been acting as a front for other Syrian financial institutions seeking to circumvent sanctions. The new penalties will prohibit the SIIB from engaging in transactions in the U.S. and will freeze any assets under U.S. jurisdiction.
Violence also continued elsewhere unabated. Syrian forces bombarded rebel-held areas in the same province where the Houla killings occurred, although no casualties were immediately reported, activists said.
Damascus had said it would conclude its own investigation into the Houla deaths by Wednesday but it was not clear if the findings would be made public.
Syria's state-run media on Wednesday denounced the diplomatic expulsions as "unprecedented hysteria."
The United States, Britain, Canada, Australia, France, Germany, Italy, Spain and Bulgaria ordered top Syrian diplomats to leave on Tuesday.
Turkey, Syria's neighbor and a former close ally, joined the coordinated protest on Wednesday. Turkey has been among the most outspoken critics of the Assad regime. It closed its embassy in Damascus in March and withdrew the ambassador. Its consulate in Aleppo remains open.
The Foreign Ministry said it ordered the Syrian charge d'affaires and other diplomats at the Syrian embassy in Ankara to leave the country within 72 hours. The consulate in Istanbul will remain open for consular duties only. Turkey also reduced the number of its personnel in the consulate in Aleppo, Syria, on Wednesday.
Turkey's Prime Minister Recep Tayyip Erdogan also said new unspecified sanctions might be imposed against Syria in the coming days. The world "cannot remain silent in the face of such a situation," he said.
Japan also ordered the Syrian ambassador in Tokyo to leave the country because of concerns about violence against civilians. Japan's foreign minister, Koichiro Genba, said his country was not, however, breaking off diplomatic ties with Syria.
The announcements came a day after the United States, Britain, Canada, Australia, France, Germany, Italy, Spain and Bulgaria ordered top Syrian diplomats to leave.
Syria's ally, Russia, criticized the diplomatic moves.
"The banishment of Syrian ambassadors from the capitals of leading Western states seems to us to be a counterproductive step," Russian Foreign Ministry spokesman Alexander Lukashevich said. He said the move closes "important channels" to influence Syria.
U.N. special envoy Kofi Annan met with Assad on Tuesday in Damascus to try to salvage what was left of his peace plan, which since being brokered six weeks ago has failed to stop any of the violence on the ground.
The Al-Baath daily, the mouthpiece of Assad's Baath Party, said Syria won't be intimidated by such "violent rhythms" and would remain standing in front of such "ugly, bloody and dramatic shows." It added that "Syria will not tremble as they think."
The government's Al-Thawra newspaper also blasted the Western decision, calling it an "escalation that aims to besiege Annan's plan and enflame a civil war."
Tensions have escalated as more information emerges about the May 25 killings in Houla.
The U.N.'s human rights office said most of the 108 victims were shot execution-style at close range, with fewer than 20 people cut down by regime shelling.
The U.N. Security Council met behind closed doors Wednesday to hear briefings from Annan's deputy Jean-Marie Guehenno and U.N. peacekeeping chief Herve Ladsous.
Ladsous said Tuesday that there are strong suspicions that pro-Assad fighters were responsible for some of the killings, casting doubt on allegations that "third elements" - or outside forces - were involved, although he did not rule it out.
"We think the last 15 months have shown that inaction by the council has led to this vicious circle of violence," Germany's U.N. Ambassador Peter Wittig told reporters as he headed into the meeting.
Meanwhile, activists said Syrian troops shelled restive suburbs of Damascus and rebel-held areas in the central city of Homs on Wednesday.
The Britain-based Syrian Observatory for Human Rights and the Local Coordination Committees said at least five people were killed in the Damascus suburb of Douma. Both groups had no details about casualties in Homs, which is the provincial capital of the province that includes Houla.
Associated Press writers Selcan Hacaoglu in Ankara, Turkey, Albert Aji in Damascus, Syria, and Edith M. Lederer at the United Nations contributed to this report.