BEIRUT: Syrian opposition chief visited rebel-held suburbs of the embattled city of Aleppo for the first time Sunday as fighters trying to oust President Bashar Assad made significant strategic advances in the heavily contested northeast.

Assad, meanwhile, lashed out at the West for sending aid to those trying to oust him, delivering a blistering rebuke to Secretary of State John Kerry's announcement earlier this week that the U.S. will for the first time provide medical aid and other non-lethal assistance directly to the fighters in addition to $60 million in assistance to Syria's political opposition.

Aleppo, the nation's largest city, has been a major front in the nearly 2-year-old conflict. Government forces and rebels have been locked in a stalemate there since July.

Mouaz al-Khatib met Sunday with Syrians living in the two rebel-held Aleppo suburbs of Manbah and Jarablus, a statement said. The stated goal of his trip to Manbah and Jarablus - the first since he was named the leader of the Syrian National Coalition late last year - was to inspect living conditions.

But his foray into the edge of Aleppo also could be an attempt to boost his group's standing among civilians and fighters on the ground, many of whom see the Western-backed political leadership in exile as irrelevant and out of touch.

The areas along the country's northern border with Turkey are largely ruled by rival brigades and fighter units that operate autonomously and have no links to the political opposition.

Al-Khatib's visit came as rebels captured a police academy west of Aleppo after an eight-day battle that left more than 200 Syrian soldiers and rebels dead, activists said. Anti-Assad fighters also stormed a central prison in the northern city of Raqqa and captured the Rabiya border crossing in the east along Syria's border with Iraq, activists said. Iraqi officials said the crossing in the country's northern Ninevah province has been closed.

The territorial gains are a significant blow to Assad, although his forces have regained control of several villages and towns along a key highway near Aleppo International Airport - an achievement that could signal the start of a decisive battle for Syria's commercial capital.

The Britain-based anti-regime group The Syrian Observatory for Human Rights said the rebels seized control of the police academy in Khan al-Asal after entering the sprawling government complex with tanks they had captured from Assad's troops in previous battles.

Observatory director Rami Abdul-Rahman said at least 120 regime soldiers and 80 rebels were killed in the fighting. He said the rebels now control all buildings inside the complex, which was abandoned by Assad's forces early Sunday.

The Syrian conflict started in March 2011 as a popular uprising against Assad's authoritarian rule, then turned into a full-blown civil war after the rebels took up arms to fight a government crackdown on dissent. The United Nations says than 70,000 people have been killed in the fighting.

Assad maintains his troops are fighting "terrorists" and Islamic extremists seeking to destroy Syria and accuses the West and its Gulf Arab allies of supporting them in achieving their goal.

In a newspaper interview published on Sunday, Assad criticized the U.S. and Britain for sending financial and other non-lethal aid to the opposition. He set harsh terms for talking to his opponents, dialing back earlier hints of flexibility about talks.

He said he is ready for dialogue with armed rebels and militants, but only if they surrender their weapons. Recently, the Syrian government offered to participate in talks, but didn't address the question of laying down arms.

"We are ready to negotiate with anyone, including militants who surrender their arms. We are not going to deal with terrorists who are determined to carry weapons to terrorize people, to kill civilians, to attack public places or private enterprise and to destroy the country," Assad told the London's Sunday Times during an interview in Damascus. "We fight terrorism."

The opposition, including fighters on the ground and the Syrian National Coalition umbrella group, has rejected talks with Damascus until Assad steps down, a demand he has repeatedly rejected.

Kerry met with Syrian rebel leaders on Thursday in Italy where he announced that the U.S. will for the first time provide medical aid and other non-lethal assistance directly to the fighters in addition to $60 million in assistance to Syria's political opposition.

Assad said the "intelligence, communication and financial assistance being provided is very lethal."

He bitterly criticized Britain, saying Prime Minister David Cameron's push for peace talks is "naive, confused, unrealistic" while his government was trying to end the European Union's arms embargo so that the rebels can be supplied with weapons.

"We do not expect an arsonist to be a firefighter," he said, dismissing any notion that Britain could help end the civil war. "How can we ask Britain to play a role while it is determined to militarize the problem?"

Britain's aim to send aid to moderate opposition groups was misguided, Assad said, adding that such groups do not exist in Syria. Arming the rebels would have grave consequences, he warned.

"We all know that we are now fighting al-Qaida, or Jabhat al-Nusra, an offshoot of al-Qaida, and other groups of people indoctrinated with extreme ideologies," he told the newspaper.