Britain is to supply armoured vehicles and body armour to Syrian opposition forces as it steps up efforts to end a humanitarian crisis of "catastrophic proportions", William Hague has said.
The Foreign Secretary said he had ordered "more active efforts" after securing a relaxation of an EU arms embargo to allow the provision of non-lethal military equipment to protect civilians.
Testing equipment to provide evidence of any use of chemical weapons by the regime and training for armed groups in international human rights and legal standards is also being sent.
He said £3 million had been allocated this month for the work in Syria with another £10 million to follow - urging other countries to do the same.
"The Cabinet is in no doubt that this is a necessary, proportionate and lawful response to a situation of extreme humanitarian suffering, and that there is no practicable alternative," he said.
"All our assistance will be carefully calibrated and monitored as well as legal, and will be aimed at saving life, alleviating this human catastrophe and supporting moderate groups."
It came as the number of refugees fleeing the country reached what he called the "sad milestone" of one million refugees.
The UK is also taking advantage of the embargo relaxation to provide assistance, advice and training to the Syrian National Coalition.
Equipment for search and rescue operations and communications will also be sent along with incinerators, rubbish collection and water purification kit to prevent the spread of disease.
Hague said the UK had fought hard to secure the changes to preserve an EU-wide approach but cautioned: "We will have to be ready to move further, and we should not rule out any option for saving lives."
It came as the chief of staff of the rebel army in Syria was in Brussels, urging the international community to supply it with arms and ammunition to help fight the regime of President Bashar Assad.
At least 10,000 people have been killed in the brutal civil war in the last two months, Hague said - more than in the whole of the first year since uprisings were brutally suppressed in 2011.
The number in need of humanitarian help inside the country has quadrupled to four million over the past 12 months - almost a fifth of the population - with a million seeking refuge in neighbouring countries.
He said he would hold talks in London with his Russian counterpart next week in a bid to secure support for a diplomatic solution - warning that Assad believed he would count on being "shielded" at the United Nations.
Russia and China have consistently vetoed Security Council resolutions critical of the regime.
"This is a situation in Syria where extreme humanitarian distress and growing dangers to international peace and security must weigh increasingly heavily in the balance against other risks," he told MPs.
"With this crisis now becoming one of major dimensions by any standard, with millions of people on the move, many tens of thousands dead, tens of thousands more in daily danger of losing their lives, the world's most volatile region in growing tension, and political deadlock that has endured for two years, our policy cannot be static nor our position indifferent."
Shadow foreign secretary Douglas Alexander said: "The primary responsibility for the violence in Syria firmly rests on President Assad's shoulders, but the ongoing humanitarian crisis represents an abject failure of the international community to act decisively and collectively.
"Today's statement by the Foreign Secretary raises more questions than it answers about the most effective way to bring the violence in Syria to an end.
"Syria today is replete with arms. The priority for the British Government should be to work to unify the Syrian opposition, not to arm it."
Earlier, International Development Secretary Justine Greening warned that women and girls risk becoming the "forgotten victims" of the crisis.
Around two-thirds of those caught up in the exodus are women and children, the majority of which are under the age of 11, aid agencies suggest.
Greening called today for international donors to deliver the humanitarian help they have pledged.
"One million refugees is a terrible landmark and the most vulnerable groups are inevitably those who find themselves at greatest risk," she said.
"Syria's neighbours cannot deal with this alone and all donors must rapidly deliver on the promises they made in Kuwait.
She spoke as the UN's refugee agency said more than 400,000 Syrians have left their homes since January, with the number registered as refugees or receiving assistance topping one million.
The UN High Commissioner for Refugees Antonio Guterres said Syria was now "spiralling towards full-scale disaster".
According to UN data, most refugees have escaped to Lebanon, Jordan, Turkey, Iraq and Egypt, with Syrians increasingly fleeing to North Africa and Europe.
Around half of those leaving their homes are young children who have lost relatives and arrive traumatised and without possessions.