(CNN) -- Syrian troops clashed with opposition fighters Friday as the battle for the capital advances relentlessly amid collapsed diplomatic efforts to impose sanctions against the regime.

Explosions rocked the Midan neighborhood in Damascus, where regime forces in tanks battled with fighters, according to opposition activists. They reported gunfire directed at people leaving a mosque in the Damascus neighborhood of Qusour. The state-run Syrian Arab News Agency said a grenade exploded in a tunnel in the capital's Umayyad Square, but no injuries were reported.

At least 26 deaths Friday in Damascus were among the 145 reported dead across the country, the opposition Local Coordination Committees of Syria said.

The government maintained its aim is to get rid of "terrorists" in the areas targeted. A Syrian security official told Al-Arabiya TV the military has started an operation to take over all neighborhoods in Damascus.

"Our heroic armed forces completely cleansed the Midan neighborhood from the remnants of the terrorists, restoring order and peace in the area," a banner on state television reported.

Protesters taking to the streets invoked the Muslim holy of month of Ramadan as their theme Friday. They chanted, "In Ramadan, victory will be written in Damascus." The holy period begins Friday in many countries.

Government helicopters shelled the suburban Damascus towns of Dumeir, Tayabiya and Harran al-Awameed, resulting in casualties and causing many people to flee, the LCC said. At least 18 people died in the Damascus suburbs, the LCC said.

Activists also reported the destruction of houses by missile fire in Aleppo and a siege of a mosque in the Daraa province town of Sanamein. At least 18 people were killed in Daraa province on Friday, the LCC said. It also reported deaths in Idlib, Hama Homs and Deir Ezzor provinces.

Syrian soldiers fought "terrorists" on Thursday night in Deir Ezzor's Bukumal city, killing and wounding dozens, the state-run news agency said Friday. The government also said that a terrorist attack on a police school in Aleppo was repelled. Forces battled "terrorists and killed most of them," the news agency said Friday.

A Free Syrian Army fighter said Friday that many soldiers and civilians were slain in fighting over the past two days in the northern rebel-held town of Saraqeb in Idlib province.

CNN cannot independently confirm reports of violence because the government restricts access by foreign journalists.

The reported fighting follows this week's U.N. Security Council deadlock over a resolution seeking to add sanctions against Syria for defying a ceasefire agreement.

Russia and China on Thursday vetoed a resolution on the Syria crisis for the third time in about 10 months, sparking international condemnation.

Susan Rice, U.S. ambassador to the United Nations, called the two countries "isolated outliers" on the issue.

Fierce fighting has raged in the capital for days, dealing a blow to the government of President Bashar al-Assad and cracking the image of invulnerability that surrounded the regime.

A blast Wednesday in Damascus claimed the lives of three top officials -- al-Assad's brother-in-law, his defense minister and a security adviser -- dealing a major blow to his inner circle.

A funeral was held Friday at the Martyrs Memorial in Damascus for the three top officials slain in Wednesday's attack.

Syrian state TV said there was a "significant official presence" at the funeral, a reference to high government officials.

Among those were Farouk al-Sharaa, the vice president, and Maher al-Assad, the president's brother and commander of Syria's Republican Guard and the Fourth Armored Division, reported Al Manar TV, the Hezbollah TV network, citing Syrian sources. The latter is helping to spearhead military operations across the country.

The head of the Syrian national bureau, Maj. Gen. Hisham Akhtiar, who was injured in the blast, died Friday, Syrian state TV said, becoming the fourth top official killed in the explosion.

In another sign of what seems to be his crumbling power, the president did not appear in public after the killings but finally showed up on television Thursday during a swearing-in ceremony for the new defense minister.

The whereabouts of the president or the location of the ceremony remain unclear, though some have suggested he is not in the capital.

Alexander Orlov, the Russian ambassador to France, told French radio Friday that al-Assad accepted a communique last month issued at a meeting of world powers in Geneva, Switzerland, calling for a governmental transition.

"So he (al-Assad) accepts to go, but to go in a civilized manner," he said. But Syrian state-media said authorities denied the report and called it "baseless." The Russian Foreign Ministry said the remarks had been taken out of context, Russia's RIA Novosti reported.

Rebels battling government forces in Damascus and its suburbs are making significant attacks on strategic border points, officials said.

Rebel fighters seeking control of the country's borders with Turkey and Iraq reported success in the latter.

The crossing points of Albo Kamal and seven additional security posts are in the hands of the rebels, a senior Iraqi army official in Anbar province said. He did not want to be named because he is not authorized to talk to the media.

Iraqi security forces have increased their military and security presence at the border in Anbar, the official said.

Travelers along the Syrian-Turkish border told CNN they saw rebels controlling border points.

At U.N. headquarters in New York, Western countries pushed for a resolution Thursday for new sanctions if Syrian government forces don't stop attacks against civilians.

The resolution also called for renewing the 300-member U.N. observer mission for 45 days after its suspension because of violence.

Russia and China -- major trade allies with Syria -- vetoed the resolution, saying they want a more balanced one that calls on all sides to halt the violence.

Competing drafts, sponsored by the United Kingdom and Pakistan, are expected to be considered by the Security Council, highlighting the simmering differences among members.

The UK mission said its resolution will be considered Friday morning. That draft measure extends the observer mission in Syria for a final period of 30 days.

Russia wants observers to stay in the country and promote dialogue, but Western countries are concerned about the safety of observers and want one final deployment.

The United Nations has estimated that more than 10,000 people have been killed in the violence since the crisis began in March 2011. Opposition groups have issued higher tolls. One prominent group, the LCC, estimates that more than 16,000 have died.

Meanwhile, Syrians fled to neighboring countries and other parts of the nation amid the relentless violence.

About 43,390 Syrians are living in camps in Turkey, the latter's disaster and emergency officials said. About 710 Syrians arrived in Turkey between Thursday and Friday, a statement said.

In Lebanon, the U.N. refugee agency said reports show between 8,500 and 30,000 people crossed into the nation in the past 48 hours.

"With the rapidly evolving situation, it is not possible to give an accurate figure of numbers of displaced persons in Syria," the U.N. refugee agency said. "As of last week, it was estimated that 1 million people may have been forced to flee inside the country since the conflict began."

Syrians are running low on resources and turning to the Syrian Arab Red Crescent and other aid groups for help, according to the relief agency.

CNN's Saad Abedine, Mohammed Tawfeeq, Ben Brumfield and Joe Sterling contributed to this report.