- NEW: Russia's foreign minister accuses some diplomats of blackmail
- International envoy Kofi Annan to meet with Russian officials on Monday
- At least 72 people were killed across Syria on Sunday, opposition activists say
- U.N. observer team: 27 villagers offered a "consistent account" about attacks in Tremseh
Are you in Tremseh in Hama province? Send photos and stories to CNN iReport.
(CNN) -- The 16-month Syrian crisis has essentially become a civil war, a Red Cross spokesman said Monday, meaning international humanitarian law would now apply "wherever hostilities take place."
The International Committee of the Red Cross officially describes the situation as a "non-international armed conflict" and does not use the term "civil war."
But spokesman Alexis Heeb said the group's legal term "appears in the Geneva Convention to describe a civil war."
"What is new is the fact that in April ... we referred to three specific locations" of internal conflict, Heeb said. Now the ICRC says the internal strife has spread.
"Rather than to limit the non-international armed conflict, we say that IHL (international humanitarian law) applies wherever hostilities take place," Heeb said.
Meanwhile, international envoy Kofi Annan will meet with Russia's president and foreign minister Monday as Annan tries to break the year-long diplomatic deadlock on Syria.
While Russia, a long-time trade partner with Syria, has vowed to stop new arms sales to the besieged country, it will not support a new U.N. Security Council draft resolution that would have more teeth against the Syrian regime.
The United Kingdom is pushing for a tough new resolution in the U.N. Security Council under Chapter 7 of the U.N. Charter. Chapter 7 resolutions are enforceable through sanctions or even military action.
On Monday, Russian Foreign Minister Sergey Lavrov accused Western diplomats of blackmail to try to force Russia to get on board with the new draft.
"Unfortunately, we have seen some elements of blackmail. We're told if we don't agree to pass the resolution (under) Chapter 7 of the U.N. charter, they will not agree to extend the U.N. observers mandate," Lavrov said at a press conference before meeting with Annan. "I consider it a totally counterproductive and a dangerous approach, because it is unacceptable to use the observers as the bargaining chip. The observers are there to assess the situation objectively."
Throughout Syria's 16-month crisis, Russia has opposed any international effort that seeks to blame, punish or change the Syrian government. Russia -- along with China -- has vetoed two previous draft resolutions in the U.N. Security Council, leading to accusations that Russia is protecting the Syrian regime.
Russian President Vladimir Putin, however, has said Russia's position is a principled one -- it is against other countries interfering in the affairs of sovereign states.
Lavrov slammed Western countries that are trying to change Russia's stance.
"The track record of those who try to make us step aside from this position has a lot of deplorable instances of unilateral military actions, and the results are well remembered by everybody," Lavrov said.
The stakes are high for world leaders to agree on a plan for Syria, with reported death tolls soaring into the dozens or hundreds in recent days.
At least 72 people were killed Sunday in cities across the country, the opposition Local Coordination Committees of Syria said.
The deaths included 11 people "martyred under torture in the regime's prisons," seven soldiers who defected, three women and six children, the LCC said.
Over the weekend, U.N. monitors visited the Syrian town of Tremseh, where opposition activists say more than 200 people were massacred on Thursday -- the deadliest day yet in the Syrian conflict.
A patrol found more than 50 houses burned or destroyed, and "pools of blood and brain matter were observed in a number of homes," the U.N. Supervision Mission in Syria said in a statement.
Twenty-seven local villagers offered a "consistent account," saying Syrian forces began by shelling the village in the early morning on Thursday, then followed with ground operations.
"According to those interviewed, the army was conducting house-to-house searches asking for men and their ID cards," the statement said.
"Numerous" people were then killed after their identification was checked, the villagers said, and some other men were taken from the village, it added.
"On the basis of some of the destruction observed in the town and the witness accounts, the attack appears targeted at army defectors and activists."
Syrian Foreign Ministry spokesman Jihad Makdissi said Sunday that what happened in Tremseh "was a military operation and not a massacre."
The Syrian regime has blamed "armed terrorist groups" for deaths in Tremseh, saying residents called security forces for help after the groups raided the town.
"Let me explain that Tremseh is a very small village that is no bigger than 1 (square) kilometer. It is quite absurd that there are some media outlets who were spreading rumors that the Syrian military dispatched 150 tanks in such a small area," Makdissi said.
Citing an unnamed source, the Foreign Ministry spokesman offered a much lower death toll from Tremseh than what opposition activists reported.
"I can't release the name of one witness, but there was someone who declared that those were killed in Tremseh were 37 militants, and only two civilians were killed," Makdissi said.
Throughout the conflict, al-Assad's regime has consistently blamed violence on "armed terrorist groups," and reported on its security forces "martyred" in attacks.
Since the Syrian crisis began in March 2011, the United Nations estimates more than 10,000 people have been killed in the violence; opposition activists say more than 15,000 have died.
Both the Syrian regime and rebels agreed to a six-point peace plan brokered by Annan earlier this year, but the plan -- which includes a cease-fire "by all parties" -- has not been fully implemented.
Though neither pro-government forces nor rebel fighters are willing to lay down their arms, cracks are emerging in al-Assad's armor.
The most senior Syrian diplomat to defect and publicly embrace his country's uprising accused the regime of collaborating with al Qaeda militants against opponents both in Syria and in neighboring Iraq.
Nawaf al-Fares, a former Syrian ambassador to Iraq, also called for foreign military intervention to topple al-Assad, as "this regime will only go by force."
"I tried during the last year and a half to convince the regime to change its treatment of the people," Fares said. "But I wasn't successful, so I decided to join the people."
CNN's Ben Brumfield, Holly Yan, Phil Black, Ivan Watson and Samya Ayish contributed to this report.
