The rebels' battles to control military outposts in Syria continued on Sunday, as the Syrian government and the opposition dismissed as unfounded allegations of secret talks between both sides.

Violent clashes in Syria renewed Sunday between the government troops and armed rebels who have been trying to storm a police academy in the country's northern province of Aleppo, activists said. While the army repulsed armed groups' attacks against outposts in several Syrian areas, local media reported.

The Sunday clashes erupted after the rebels launched fresh offensive against the police academy in the Khan al-Asad town to the west of Aleppo, said the Britain-based Syrian Observatory for Human Rights.

It said the rebels managed to storm the academy's fence from several directions, adding that the clashes witnessed mutual bombardment with mortar and tank shells.

The observatory reported losses from both sides, saying that the facility has been besieged by the rebels.

The pro-government al-Khabar TV also confirmed the clashes at the academy "that have been raging for the third straight day." It said the academy's troops backed with artillery firepower succeeded in repulsing the attack at noon Sunday, adding that heavy losses were inflicted upon the rebels.

Meanwhile, the state-run SANA news agency said Syrian troops foiled on Sunday the attempts of armed groups to infiltrate from the Lebanese territories into Syria through the border town of Talkalakh near Syria's central city of Homs.

Quoting an official source, SANA said the infiltrators were pouring in from the Lebanese areas of al-Muqelbieh, al-Hisha and al-Rama, adding that the assailants opened fire from their machine- guns and rocket shells at the Syrian border guards who returned fire and inflicted hefty losses upon them.

In the northwestern province of Idlib, the Syrian army repulsed an armed groups attack at military checkpoints at the vicinity of Wadi al-Dayf military site, and the troops dealt big blows to the attackers.

The Syrian army also repelled a rebels' attack on a military checkpoint in al-Nabik area just outside Damascus, SANA said.

The rebels have escalated their offensives over the past couple of months in the hope of achieving gains on ground before engaging into possible negotiations.

Speaking about negotiations, the head of the broad-based Syrian National Coalition (SNC), the main opposition umbrella, denied reports alleging that he had made contacts with representatives of the Syrian government.

On his Facebook page, Moaz al-Khatib stated Sunday that he did not contact officials or Syrian businessmen regarding future negotiations with the government of President Bashar al-Assad.

The dismissal came one day after his coalition announced that it would not attend next month's Friends of Syria meeting in Rome. Meanwhile, Syrian Information Ministry dismissed the talks' reports as unfounded as well.

The SNC, formed in Doha in November last year, said the planned boycott was in protest against a lack of international condemnation of the "crimes committed against the Syrian people."

Last month, al-Khatib announced his readiness to embark on " negotiations" with representatives of the Syrian government "whose hands weren't smeared in Syrians' blood."

He said the talks should result in the departure of the administration. However, the Syrian government did not respond to al-Khatib, but stated that it would not accept pre-conditions prior to the dialogue.

For his part, joint UN-Arab League envoy to Syria, Lakhdar Brahimi, hailed al-Khatib's move, urging both sides to engage into initial talks at the UN headquarters. But the Syrian government has repeatedly said any dialogue should be held on the Syrian soil and accused Brahimi of being biased.

Syria has been witnessed unrest for nearly two years. UN human rights chief Navi Pillay has placed the death toll from Syria's long-standing turmoil at nearly 70,000.