Actor Michael Sheen has spent time with Syrian refugees at a large camp in Lebanon but warns that cold weather presents a real threat.
The Government will urge for international action to protect women and girls from violence and sexual exploitation in emergency situations.
The violence in Syria threatens an uneasy truce in neighbouring Lebanon where guns have reappeared on the streets after years of peace.
Lebanese authorities have identified the second suicide bomber who attacked the Iranian embassy in Beirut this week as a Palestinian man with ties to a fugitive Lebanese Islamist cleric, a security source has told Reuters.
At least 23 were killed and 146 wounded following the blasts targeting the Iranian Embassyon Tuesday, according to the Lebanese health minister.
Lebanese authorities had identified the first suicide bomber a day earlier as a Lebanese man with ties to hardline Sunni Muslim groups.
The source said the second bomber, who lived in southern Lebanon, was a follower of Ahmed al-Assir, a firebrand Sunni Muslim cleric whose militant supporters fought a two-day battle with the Lebanese army in June after barricading themselves in a mosque in the southern port city of Sidon.
The US has condemned a suicide bombing that killed at least 23 people near an Iranian embassy compound in Beirut.
White House spokesman Jay Carney said at a briefing: "We call on all parties to exercise calm and restraint to avoid inflaming the situation further."
"Acts of terror only reinforce our determination to work with the institutions of the Lebanese state."
But he added that it was too soon to say who was responsible for the attack.
Forensic experts have been inspecting the sites of two suicide bombings which killed at least 23 people and wounded 146 near the Iranian embassy in Beirut.
Lebanese officials said CCTV footage showed a man in an explosives belt rushing towards the outer wall of the embassy before blowing himself up.
The second, larger explosion was the result of a car bomb, although the Lebanese army said it is treating both blasts as suicide attacks.
Foreign Secretary William Hague has condemned what he describes as a "shocking terrorist attack" after at least 23 people were killed following blasts near the Iranian Embassy in Beirut.
– Foreign Secretary William Hague
I strongly condemn the shocking terrorist attack on the Iranian embassy in southern Beirut today that has led to such tragic loss of life. I send my condolences to the families of those killed and injured. The UK is strongly committed to supporting stability in Lebanon and seeing those responsible for this attack brought to justice.
Our Embassy in Beirut remains at a high state of vigilance. A consular team stands ready to assist British nationals.
A Lebanon-based al-Qaeda affiliate has claimed responsibility for the double suicide attack on the Iranian embassy which killed 23 people, according to the Twitter page of a cleric linked to the group.
"The Abdullah Azzam brigades - the Hussein bin Ali cells - may they please God - are behind the attack on the Iranian embassy in Beirut," Sheikh Sirajeddine Zuraiqat, the group's religious guide, posted on Twitter.
The group threatened to carry out further attacks until Iran pulled its forces out of Syria and their prisoners were released from Lebanese jails.
Footage from security cameras has shown a man rushing towards the outer wall of the Iranian embassy before causing the first explosion in the area, Lebanese officials have told Reuters.
The second explosion was caused by a car bomb parked two buildings away from the embassy, officials said.
Twenty-three people have been killed in the two blasts including the Iranian cultural attache.
The Iranian cultural attache is among the 23 people who have been killed after two explosions near the Iranian embassy in Beirut.
A Lebanese official told Reuters that Ebrahim Ansari was killed in the explosions.
Health minister Ali Hassan Khalil said the blasts had also wounded 146 people.
Twenty-three people have been killed following two explosions near the Iranian embassy in Beirut, Reuters have reported.
A witness at the scene said he saw body parts scattered around the blast site.
"At one entrance of the Iranian embassy I counted six bodies outside. I saw body parts around and thrown two streets away," Reuters television cameraman Issam Abdullah said from the scene.
"There is huge damage, it looks like it is a car bomb. One car is twisted there. There were two Mercedes cars badly damaged," he added.
At least 23 people have been killed and 146 wounded following blasts near the Iranian embassy in Beirut, according to the Lebanese health minister.
Debris was scattered across the street and cars were on fire as people ran away from the chaotic scene.