Lebanese intelligence officers were questioning the crew of a Sierra Leone-flagged vessel on Sunday over allegations it was carrying arms to Syrian rebels as fighting raged between the insurgents and regular troops.
Ten rebel fighters were among 32 people killed on Saturday as bloodshed persisted more than two weeks into a promised UN-backed truce, the Syrian Observatory for Human Rights said.
The interception of the ship by Lebanon -- currently governed by a largely pro-Syrian coalition -- gave grist to Russian opposition to the tough Western and Arab line taken against its longtime Middle East ally.
Lebanon said it had intercepted three containers of heavy machineguns, artillery shells, rockets, rocket launchers and other explosives destined for rebel forces on a ship originating in Libya.
Syrian authorities have repeatedly charged that weapons are being smuggled from Lebanon to rebels.
On Saturday, government newspaper Tishrin wrote that UN chief Ban Ki-moon "avoids talking about abuses by armed groups and focuses his blame solely on Syria, as usual. He encourages these groups to continue to commit more crimes and terrorist acts."
The Russian foreign ministry said "we are convinced that the terrorists operating in Syria need a decisive rebuff, and that all domestic and outside players need to prevent any support" from reaching the rebel forces.
Government troops killed at least 10 rebel fighters in the Damascus region on Saturday, the Britain-based Syrian Observatory said.
Twenty-two civilians also died -- eight in flashpoint central Hama, two in nearby Homs, three in Idlib near the Turkish border, four in Aleppo, four in Damascus province and one in Al-Raqqah in the northeast.
Separately, the official SANA news agency reported three soldiers and two "terrorists" killed in Syria's second-biggest city Aleppo in clashes between troops and "armed terrorist groups."
An activist said the fighting began as "officers and soldiers of a military base near the presidential palace... deserted with their weapons."
And in what was believed to be the first case of Westerners going missing in the violence-swept country, Budapest said two Hungarians had been kidnapped.
A putative truce, which technically came into effect on April 12, has taken a daily battering, and the European Union on Friday expressed extreme concern about the persistent bloodshed.
The latest violence came as veteran Norwegian peacekeeper Major General Robert Mood was en route for Syria to take the helm of a fledgling monitoring mission after being appointed by UN chief Ban Ki-moon, diplomats said.
Mood takes over a mission already facing major obstacles before the full 300-member force approved by the UN Security Council has even gathered.
He has himself highlighted the "abyss of suspicion" between President Bashar al-Assad and the opposition, in the face of an uprising that has killed more than 9,000 people since March 2011, according to UN figures.
Mood "is on his way to Damascus and arrives there tomorrow," Sunday, international peace envoy Kofi Annan's spokesman Ahmad Fawzi told AFP in Geneva.
Saturday's violence came the day after a suicide car bombing in Damascus that the Observatory said killed two and Syria's state media said killed 11.
The opposition blamed government forces for the bombing and demanded an international inquiry.
"The Syrian National Council condemns this criminal act which is aimed at further undermining the security and stability of our country and at terrorising our people," a statement said.
After the Damascus blast, SANA quoted the interior ministry as saying "it will not tolerate the armed terrorist groups and vowed to strike with an iron fist those who are terrorising citizens."