Syria vowed to hold "free and transparent" polls later this year but re-arrested a leading dissident, as foreign pressure mounted over its deadly suppression of anti-regime protests.
Security forces arrested prominent opposition figure and former political prisoner Walid al-Bunni and his two sons, Syrian Observatory for Human Rights chief Rami Abdel Rahman said.
The arrests came just hours after Damascus Saturday vowed to hold "free and transparent" elections by the end of 2011.
In 2000, Bunni was one of the prime movers of the short-lived "Damascus Spring" amid hopes for reform after Bashar al-Assad became president following the death of his father Hafez.
Abdel Rahim said earlier that hundreds of tanks and armoured cars had been deployed in the northeastern city of Deir Ezzor and around Homs in central Syria.
"Syria will hold free and transparent elections that will give birth to a parliament representing the aspirations of the Syrian people," Foreign Minister Walid Muallem said in a meeting with ambassadors posted to Damascus.
"The general elections will be held before the end of the year," Muallem said, quoted by the official SANA news agency.
The foreign minister stressed "the commitment of the Syrian leadership to the continued reform process and implementation of measures announced by Assad."
UN leader Ban Ki-moon told Assad, who has been refusing to take his calls, to immediately end his deadly military campaign against opponents.
"In a phone conversation with President Assad of Syria today, the secretary general expressed his strong concern and that of the international community at the mounting violence and death toll in Syria over the past days," said UN spokesman Martin Nesirky.
Ban "reflected to the Syrian president the clear message sent by the Security Council and urged the president to stop the use of military force against civilians immediately," Nesirky said.
The embattled president issued a decree on Thursday allowing opposition political parties, but the move was largely dismissed by the opposition as a ploy to appease protesters.
The oil-rich Arab monarchies of the Gulf on Saturday turned up the heat on Damascus, with the six-nation Gulf Cooperation Council calling in a statement for an "immediate end to violence... and bloodshed."
They urged a "resort to wisdom and introducing serious and necessary reforms."
Their call followed a pledge by the US, French and German leaders to consider new steps to punish Syria after a deadly crackdown on the first Friday of Ramadan, the holy Muslim month of fasting.
President Barack Obama spoke separately to France's Nicolas Sarkozy and German Chancellor Angela Merkel as Western nations cranked up pressure on Assad.
They "condemned the Assad regime's continued use of indiscriminate violence," the White House said. They "also agreed to consider additional steps to pressure the Assad regime and support the Syrian people."
The Syrian government has sought to crush the democracy movement with brutal force, killing around 1,650 civilians and arresting thousands of dissenters, according to the Syrian Observatory for Human Rights.
Abdel Rahman of the Syrian Observatory said around 250 tanks and armoured cars were deployed in four districts of Deir Ezzor on Saturday.
The tanks were also posted around the airport in Deir Ezzor, many of whose residents started to flee the city from Wednesday, fearing imminent military action.
In Homs, "many armoured cars and other army vehicles have been posted in the Bab al-Sibaa district," Abdel Rahman said, adding that activists in the city reported gunfire from early morning.
Communications have been cut off as the army stepped up an operation to crush dissent in Hama, the central city where security forces killed at least 30 civilians and wounded dozens more earlier in the week.
The call for Friday's protests came from activists on Facebook group The Syrian Revolution 2011, a driving force behind the demonstrations that have been calling for greater freedoms since mid-March.