The Syrian government has said that it will co-operate with the visit of UN humanitarian chief Valerie Amos, who is seeking access to anti-government districts that have been battered by a violent crackdown on protests.

Walid Muallem, the Syrian foreign minister, told Amos during a meeting on Wednesday that his government was attempting to provide food and medical assistance to those in need, despite "the burden it faces as a result of unfair sanctions imposed by some Western and Arab nations which are affecting the population".

He "underlined Syria's commitment to cooperate with the delegation within the framework of the respect, sovereignty and independence of Syria and in coordination with the foreign ministry," the state SANA news agency reported.

The United Nations' under-secretary-general for humanitarian affairs arrived in Damascus earlier on a two-day mission aimed at getting government and opposition approval for relief workers to access civilian areas badly hit during the violent unrest that has accompanied a movement against Bashar al-Assad, the Syrian president.

Amos, whose request to visit Syria was rejected earlier this month as government forces bombarded an opposition stronghold in Homs, is due to hold talks with senior government officials from Wednesday until Friday.

The aim of her visit is "to urge all sides to allow unhindered access for humanitarian relief workers so they can evacuate the wounded and deliver essential supplies," according to Amos.

Amos' arrival comes days before Kofi Annan, a joint UN-Arab League envoy appointed to find a way to end the violence in Syria, is due in Damascus.

Li Huaxin, a Chinese diplomat, is also currently in the Syrian capital, where he held talks with Muallem on Wednesday in which the two discussed Beijing's six-point plan for halting the violence.

Amos' trip comes amid reports of growing numbers of Syrians fleeing the government's crackdown into neighbouring Lebanon, with at least 2,000 people crossing the border in the past two days, according to the UN refugee agency.

Syrian President Bashar al-Assad faces mounting international pressure over his government's apparent refusal to allow medical aid into the devastated, largely anti-government Homs district of Bab Amr, in addition to alleged rights abuses by government forces.

Dozens of men, women and children have returned on foot to Bab Amr, passing buildings riddled with bullet holes and other damage.

The return comes days after opposition fighters pulled out of the neighbourhood following a sustained heavy military assault.

'Smell of death'
The International Committee of the Red Cross (ICRC) says it is still awaiting approval to distribute aid in Bab Amr after the month-long siege.

Residents who fled the district spoke of bodies decomposing under rubble, sewage mixing with litter in the streets, and a campaign of arrests and executions.

"The smell of death was everywhere. We could smell the bodies buried under the rubble all the time," Ahmad, who escaped to Lebanon, said.

"We saw so much death that at the end the sight of a dismembered body ... stopped moving us."

Fresh violence was reported by activists in the provinces of Homs, Deraa, Idlib, and Deir ez-Zor on Tuesday.

The Local Co-ordination Committees, an umbrella organisation of opposition activists, claimed that at least 21 people were killed in that violence.

Rami Abdel Rahman, head of the UK-based opposition Syrian Observatory for Human Rights (SOHR), said government forces bombed a bridge used to evacuate the wounded and refugees to Lebanon from Homs.

The SOHR also reported that at least 12 people - including five government troops - had been killed in clashes in the town of Herak, in Deraa, after a major government assault on the town.

Al Jazeera is unable to independently verify the activists' claims because of restrictions on reporting imposed by the government.