Fighting in Syria has seen a missile strike near the country's biggest city, Aleppo, kill 26 people and government fighter jets target the rebel-held town of Qusayr, according to reports.
The Syrian Observatory for Human Rights (SOHR), the activists' network, said on Tuesday there were numerous dead on both sides but gave no other details.
US-based group Human Rights Watch, meanwhile, said its mission to Aleppo had concluded that the bodies of 147 men pulled out of a local river between January and March were "probably" executed in government-controlled areas of the city.
The SOHR also said shellfire near the Russian embassy in Damascus had killed a civilian and wounded a member of the security forces.
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A representative of the Russian embassy in Damascus told AFP news agency two Syrian security guards had received injuries but that no embassy staff had been killed or hurt in the attack.
The besieged Syrian town of Qusayr came under renewed missile and air attack on Tuesdasy as fighting there dragged into a third week.
The situation in the strategic town near the Lebanon border prompted fresh calls for humanitarian access to offer some relief to the thousands trapped by government forces.
Syrian soldiers have mounted a fierce onslaught on Qusayr, in Homs province, and also slightly farther north in Dabaa, the site of a disused military airbase partly under rebel control.
Syrian troops backed by Lebanon's Hezbollah fighters have besieged the town, which controls vital supply routes from Lebanon and access between Damascus and the coastal heartland of President Bashar al-Assad's minority Alawite sect.
As Syrian government forces try to wear down the rebels in Qusayr, trapped civilians have had to choose between sheltering from the bombs or risking a 100km journey to safety.
"Qusayr itself is described as a ghost town, heavily damaged and filled with the sound of bombs. People are hiding in bunkers or, even worse, in holes that they've dug," Melissa Fleming, UN refugee agency spokeswoman, told a briefing in Geneva, Switzerland, on Tuesday.
"One woman told us that she spent, with her children, one week inside a hole that was dug into the ground."
Opposition leaders called for the creation of a humanitarian corridor to allow people from Qusayr to flee to Lebanon.
The International Committee of the Red Cross said the Syrian government had said it was willing to grant the agency access to Qusayr once military operations there had ended
A doctor in Qusayr told Al Jazeera this week there were now more than 1,000 injured people in the town and conditions were becoming increasingly dire.
Kassem al-Zein, who coordinates treatment in several makeshift hospitals, said the wounded were being treated in private homes after the town's main hospital was destroyed.
"Four days ago, some of the injured were taken outside the city but they were hit by the forces of the regime. Some of the injured returned back to us with more injuries," he said.
"It is a serious catastrophe. The martyrs are more than 200. We have no time to bury them. Some stayed for days in the streets. The smell of death is all over the place, it is not human.
"Where is the world, where are the organisations who are claiming to help the people? We have lost everything."