BEIRUT -- The widowed Syrian mechanic had a new lease on life after he married his second wife: he enrolled in a high school, graduating at 60. The couple had five children, living in an impoverished quarter of a town in northern Syria.

They all died after a missile smashed into their building overnight in the town of Marea, in all killing 13 people, most of them children, Syrian opposition activists said Tuesday.

That attack was followed hours later by a missile fired at a building in the nearby town of Azaz that killed another 10 people.

The strikes were reported on Tuesday by local activists, said the Britain-based Syrian Observatory for Human Rights and the activist collective, the Aleppo Media Center. They are the latest victims of Syria's civil war and the government's relentless bombing campaign against opposition-held territories in northern Syria.

The story of Mohammed Jafar Saleh, 70, is a human sketch of one of the 162,000 people estimated killed in Syria's civil war, now entering its fourth year.

Saleh's first wife died over 15 years ago, said an activist from Marea who identified himself as Abu al-Hassan.

The man remarried soon after, to a young woman, Mufida Rasoul. She was 40 when she died overnight. Their five children ranged from Abir, 14, to Rahaf, 4, both girls.

Abu al-Hassan said the marriage seemed to revive the man, who had a shop fixing broken car radiators. He enrolled in a school for older students, earning a high school diploma after 10 years instruction, the activist said.

"He wanted to go to university but his grades weren't very good," according to Abu al-Hassan, who said he used to attend annual exams with the man.

Nothing was left of the family.

The severed legs and waist of a boy pulled from the rubble, shown in footage uploaded to social networks by activists, may have belonged to one of the Saleh children. The footage appeared genuine and corresponded with Associated Press reporting of the event.

The 13 dead were mostly children, according a list of their names and ages, distributed by another activist in Marea.

Another two of the slain children, Mohammed, 7, and Usama, 9, were the sons of a school teacher named Hussein Hajj Ali, said Abu al-Hassan.

Video footage showed the school teacher, wild eyed, swaying and moaning as he was bought into a clinic, his arm bandaged. He was weeping for his son Mohammed as medics rushed a blanket-wrapped body past him.

As the medics treated him, he chanted a poem that speaks of the grief of losing a child.

"Death has chosen my middle child. For God's sake how could he choose the best stone of the necklace," Hajj Ali wept, quoting the lines of the poet Ibn al-Roumi, who lived in ninth century Baghdad.

At the time, the teacher did not know he had lost both sons -- his middle son and his youngest -- said Abu al-Hassan, who said he spoke later to medics.

The teacher had avoided politics, fearing the Syrian government would cut his meagre salary if he expressed any support for the uprising against President Bashar Assad, the activist said.

Abu Al-Hassan said he wasn't aware of any fighting in the area, known as Haret Beit Faraj, which lies near an outdoor market. He said the nearest front was 15 miles away (25 kilometres) in the area of Bureij.

Rights groups and local activists say Syrian military forces often indiscriminately strike rebel-held areas with projectiles that can't be targeted properly, overwhelmingly killing civilians.

But usually such attacks happen when government forces are trying to clear out a rebel-held area.

Also Tuesday, The joint mission of the U.N. and The Organization for the Prohibition of Chemical Weapons confirmed the destruction of the entire declared Syrian stockpile of a chemical called Isopropanol.

Under a destruction plan approved by the OPCW in November, Syria also was required to destroy its stocks -- estimated at around 100 tons -- of isopropanol, which can be used as an ingredient of sarin.

In a statement, the mission said 7.2 per cent of Syria's chemical weapons material remains in country and awaits swift removal for onward destruction. "The Joint Mission urges the Syrian authorities to undertake this task as soon as possible," it said.

Following a deadly chemical attack outside Damascus in August, the Syrian government averted U.S. airstrikes by agreeing to dismantle its chemical program. The U.N.-OPCW mission overseeing the removal of Assad's chemical arsenal said last week that 92 per cent of Syria's stockpile has been transported to Danish and Norwegian ships for destruction at sea. The entire stockpile is to be purged by the end of June.

In Moscow, Deputy Foreign Minister Gennady Gatilov was quoted as telling news agency Interfax that Russia would veto any U.N. Security Council resolution aimed at sending material about Syrian war crimes to the International Criminal Court.

"The draft submitted to the UN security council is unacceptable and we will not support it. If it is put to a vote, we will veto it," Gatilov said Tuesday. "We have said from the very beginning that we are against such an approach in the Security Council because we consider it to be counterproductive in the current situation."

Gatilov's comments came a day after nearly 60 countries urged the U.N. Security Council to refer the war in Syria to the International Criminal Court for investigation of possible crimes against humanity and war crimes.

Associated Press writer Jim Heintz contributed to this report from Moscow.