Activists say 20 people have been killed by security forces across Syria, as protesters took to the streets under the slogan "death rather than humiliation".
The Syrian Observatory for Human Rights said eight people were killed when security forces intervened to disperse protests in several suburbs of Damascus, including Douma and Arbeen, on Friday.
Three other people died in Homs province and three in the eastern city of Deir ez-Zor, the UK-based group said.
It was not immediately clear where the other casualties occurred.
An activist told Al Jazeera that there was a heavy security presence in Deir ez-Zor, with troops and tanks deployed by the city’s entrances.
"We will not stop the demonstrations until we see the president in jail," he said.
Activists said the largest protest turnout was in Homs, where a funeral turned into a massive anti-government demonstration. Thousands of people were taking part, calling for the regime's downfall and for President Bashar al-Assad's execution, witnesses said.
One of Friday's rallies was held in support of a senior official who resigned this week to protest against the regime's crackdown on protesters.
The Local Co-ordination Committees (LCC) said demonstrators rallied outside the home of Mohammed Adnan al-Bakkour, the attorney-general of Hama who announced his resignation in a contested YouTube video.
Bakkour said he resigned in disgustat hundreds of killings, torture and arrests, but authorities said he quit under duress after being kidnapped.
Earlier on Friday, European Union governments agreed to ban imports of Syrian oil in a move to strengthen economic pressure on Assad and his government.
EU foreign ministers met in Poland on Friday, where they discussed a plan first announced two weeks ago to impose sweeping new economic sanctions against Syria, including an embargo on oil imports.
David Cameron, the British prime minister, expressed his support for new sanctions against Damascus on Thursday following the "Friends of Libya" conference in Paris.
In-depth coverage of escalating violence across Syria
"We need tougher sanctions, more travel bans, more asset freezes, a clear message that the regime and what it is doing is unacceptable," he said.
The oil embargo marks a significant step for the EU, which has so far taken an incremental approach to sanctions against Assad as they try to force him to end a crackdown on anti-government protesters and relinquish power.
Friday's decision also expanded the list of entities subject to EU travel bans and asset freezes by seven, including four people.
"The sanctions have been agreed," an EU official told the Reuters hews agency. "They ban the import of Syrian oil and petroleum products to the EU. Four more people and three entities are also included."
The measures will go into effect on Saturday.
International pressure appears to have had little effect on the Syrian leadership, which intensified its crackdown on protests in August.