Syrian President Bashar al-Assad should heed U.S. warnings to neither use nor move chemical or biological weapons , lest he risk crossing a `` red line '' and provoke a U.S. military response , President Barack Obama said Monday . `` We can not have a situation where chemical or biological weapons are falling into the hands of the wrong people , '' Obama told reporters at the White House . `` We have been very clear to the Assad regime -- but also to other players on the ground -- that a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized . `` That would change my calculus ; that would change my equation . '' Obama added that U.S. officials are monitoring the situation `` very carefully '' and have put together a number of contingency plans . Saudi support for Syrian rebels shaped by tribal , religious ties . `` We have communicated in no uncertain terms with every player in the region that that 's a red line for us and that there would be enormous consequences if we start seeing movement on the chemical weapons front or the use of chemical weapons . '' Obama 's remarks appeared to ratchet up his stance on the matter . Last month , talking about Syrian forces , he told a VFW convention , `` They will be held accountable by the international community and the United States should they make the tragic mistake of using those weapons . '' The Syrian regime `` probably has the largest and most advanced chemical warfare program in the Arab world , '' Michael Eisenstadt , director of the military and security studies program at the Washington Institute for Near East Policy , told CNN last month . It includes `` thousands of tube and rocket artillery rounds filled with mustard-type blister agents , thousands of bombs filled with the nerve agents sarin and possibly VX , and binary-type and cluster CW warheads filled with nerve agents for all its major missile systems . `` Its CW infrastructure is believed to include several production facilities and numerous storage sites , mostly dispersed throughout the western half of the country , '' Eisenstadt said . Syria is thought to have a biological warfare research and development program , but is not known to have offensive biological warfare agents , Eisenstadt said . The nation is not a party to the Organization for the Prohibition of Chemical Weapons . That 's the body of the Chemical Weapons Convention dedicated to eliminating the weapons . Israeli President Shimon Peres has said his country too is preparing contingency plans to attack Syria 's chemical weapons arsenal if Israel is directly threatened . In September 2007 , Israeli jets bombed a building in Syria that the U.N. nuclear agency eventually concluded was `` very likely a nuclear reactor . '' Obama 's warning on Monday came as Muslims in Syria celebrated the second of three days of feasting to honor the end of the holy month of Ramadan , with the holiday 's message of amity and tolerance contrasting sharply with reality . U.N. observer mission in Syria ends , violence continues . At least 150 people were killed Monday , including two children and their mother in Daraa , the opposition Local Coordination Committees of Syria said . A Japanese journalist was killed during a gun battle in Aleppo , the Japanese foreign ministry said Tuesday . Mika Yamamoto , 45 , worked for the independent Japan Press news agency and had been reporting on the Free Syrian Army . Her body was taken to Turkey , where officials were working to get more information , the ministry said . Also among the dead in Syria were 10 bodies discovered splayed on the ground in the Damascus suburb of Qaboun . Video posted by activists showed at least one of the victims lying on his back , blindfolded , his arms stretched above his head . Others showed victims with bruised flesh and dark red splotches on their clothes . CNN can not authenticate the video . Another video , said to have been shot Sunday in the town of Talbeesa , north of Homs , showed children being pushed on swings . The swings are attached to the gun of a tank on which adults are standing , chanting , `` Victory for the rebels ! '' In a third video , showing the same tank , a man says to the camera , `` We will enter Homs with this tank and liberate all of Syria , God willing ! '' Daraa province , where the conflict began in March 2011 as peaceful anti-government demonstrations , has suffered heightened violence in recent days . It is also the home province of Vice President Farouq al-Sharaa , who rebels say has defected from the regime . On Sunday , the charred bodies of 20 people were discovered in the Daraa city of Hirak , and 31 other people were killed in the province , the LCC said . Government forces executed 14 people in Daraa hours after they were detained , the opposition network said . Hirak took another beating Monday , when mortars and rockets rained down on the city , the LCC said . Inside Syria : Nobody imagined it would turn into this . Since the Syrian crisis began 17 months ago , more than 20,000 people -- most of them civilians -- have been killed , opposition activists say . Complete coverage of CNN Inside Syria .
A Japanese journalist is killed , the government says Tuesday . At least 150 people were killed across Syria on Monday , opposition activists say . Score: 7