UN chief rejects asylum deal for Assad Free Syrian Army fighters with rocket-propelled grenades in the Al-khalidiya neighbourhood of Homs The UN secretary-general has suggested that he would not approve any asylum deal for Syria's President Bashar al-Assad as a way to end the country's civil war in which rebel forces appear to have made advances in recent weeks. Ban Ki-moon told the Associated Press on the sidelines of the UN climate change conference in Doha that the world body does not grant anyone "impunity." Whoever commits [a] gross violation of human rights must be held accountable and should be brought to justice. This is a fundamental principle," Mr Ban said. Recent victories by rebels have claimed key infrastructure and military bases. And in a fresh sign that opposition forces are making inroads in and around Damascus, one of the rebel groups claimed to have surrounded an air base in the capital on Wednesday, according to Reuters. Those recent gains by opposition forces has raised fears in the west that the Assad regime could either resort to the use of chemical weapons to regain lost ground, or could lose them to one of the disparate rebel groups. The Obama administration this week warned that it had "increased concerns" about the possibility of this, to which Damascus reiterated its promise not to use the weapons against Syrians. Hillary Clinton, the US secretary of state, repeated those concerns on Wednesday. She was speaking after Nato agreed to send Patriot anti-missile equipment to Turkey, to defend it from a possible missile attack from neighbouring Syria. "Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons, or might lose control of them to one of the many groups that are now operating within Syria," Mrs Clinton said. And so as part of the absolute unity that we all have on this issue we have sent an unmistakable message that this would cross a red line and those responsible would be held to account. Mr Ban added: "I again urge in the strongest possible terms that they must not consider using this kind of deadly weapons of mass destruction. I have warned that if in any case this should be used, then there will be huge consequences. And they should be accountable. Nato's decision to send Patriot missiles to Turkey comes as evidence builds that the civil war, which has claimed more than 40,000 lives and displaced hundreds of thousands more, is spilling over into neighbouring countries. To the Turkish people we say: We are determined to defend you and your territory. To anyone who would want to attack Turkey we say: Don't even think about it," said Anders Fogh Rasmussen, Nato secretary-general. A second day of fighting in Lebanon's northern port city of Tripoli on Wednesday claimed the life of one man and injured 39, Reuters reported. Two days of violence has left four people dead and injured 39, the agency said. The Lebanese army has blocked roads leading to the area and has sent in reinforcements to try and stop the violence along Syria Street, the main road that has seen most of the spillover fighting over the past year, Reuters said. Reuters said the deaths of at least 14 Lebanese and Palestinian gunmen in a Syrian border town late last week instigated the violence in Tripoli, which is a majority Sunni city mostly supporting the uprising next door but also has an Alawite minority. The Lebanese government has demanded the return of the bodies of those who were killed.