Forces loyal to Syrian President Bashar al-Assad have launched an assault on the southern city of Deraa, intensifying efforts to crush a year-long uprising in the country.

With the anniversary of the revolt falling today, the Syrian army appears to have multiplied attacks on opposition strongholds, sending up to 130 tanks and armoured vehicles to the city.

The city lies close to Jordan and was the site of some of the first protests against Assad a year ago.

Regime forces have also seized Idlib in northwestern Syria from rebel control.

Noureddin al-Abdo, an activist in Idlib, confirmed that the city had fallen after a four-day assault by regime forces.

The "Free Syrian Army has withdrawn and regime forces have stormed the entire city and are carrying out house-to-house searches," said Mr al-Abdo told AFP.

The army launched its assault on the rebellious province of Idlib near the Turkish border on Saturday, bombarding the city of the same name and outlying areas in a bid to root out armed insurgents.

The Syrian Observatory for Human Rights said fierce clashes between regime forces and rebel troops were still raging in the Jabal al-Zawiya district of the province, while at least 10 people had been killed across the country.

The capture of Idlib comes two weeks after regime forces stormed the Baba Amr rebel stronghold in the central city of Homs following a month-long blitz that left hundreds dead.

The United Nations estimates some 8,000 people, many of them civilians, have died in the increasingly violent months that followed.

Syrian detainees face 'torture nightmare'

Detainees in Syria's year-old crackdown on dissent face a "nightmarish world of systematic torture" that has set the country back decades, Amnesty International has warned in a new report.

"The scale of torture and other ill-treatment in Syria has risen to a level not witnessed for years and is reminiscent of the dark era of the 1970s and 1980s," the group said in a report based on testimony from survivors who fled to Jordan.

Ann Harrison of Amnesty's Middle East and North Africa programme said the experience is very similar to that of detainees under former president Hafez al-Assad.

The report points to 31 methods of torture or other ill-treatment by Syrian security forces and their "shabiha" militia allies.

The report said many victims reported that the beatings began on arrest and then they were beaten severely, including with sticks, rifle butts, whips and fists, braided cables, on arrival at detention centres.

It said testimonies of 25 people who reported having been tortured or otherwise ill-treated indicated prisoners were most at risk when under interrogation.

Ms Harrison said the testimonies amounted to "yet more evidence of crimes against humanity in Syria."

Amnesty called for the UN Human Rights Council to extend the mandate of its Commission of Inquiry on Syria "and reinforce its capacity to monitor, document and report, with a view to eventual prosecutions."

Annan says more questions must be addressed

International peace envoy Kofi Annan, said he had received President Assad's response to proposals which he submitted in talks with the Syrian leader last week but had more questions which needed to be addressed without delay.

While Russia, which is seen as a Syrian ally, criticised President Assad for his "big delay" in implementing reforms, at the risk of escalating the crisis.

In a rare public rebuke from Moscow to the Syrian leader, Russian Foreign Minister Sergei Lavrov accused President Assad of "inertia."

"The side in the conflict in Syria on which we have influence is the government of Bashar al-Assad. Unfortunately, his actions, in practical terms, reflect our advice far from always and far from swiftly," Mr Lavrov said.

Members of SNC resign

The Syrian opposition not only suffered setbacks on the military front, but also politically as the Syrian National Council coalition was hit by resignations.

Haitham al-Maleh, Kamal al-Labwani and Catherine al-Talli announced that they quitting on their Facebook pages, blaming "differences" and the "inefficiency" of the SNC.

Mr Labwani launched a scathing attack on the coalition formed last August in Istanbul to fight a political battle against President Assad.

He said the trio had resigned because they did not want to be "accomplices to the massacre of the Syrian people through delaying, cheating, lies, one-upmanship and monopolisation of decision-making."

Guardian claims to have obtained President's emails

Meanwhile, British newspaper The Guardian has published emails it claims were sent by President Al-Assad and his wife, allegedly revealing the regime sought advice from Iran on suppressing protests.

The newspaper admits it "is impossible rule out the possibility of fakes" in the cache of over 3,000 emails, which appear also to reveal the lavish lifestyle enjoyed by the leader and his wife, Asma.

The newspaper stressed it had made "extensive" efforts to authenticate the emails, which it says were intercepted from the couple's private accounts and passed on by a source in the Syrian opposition.

The messages, published on the paper's website, appear to show that Assad received advice from Iran or its proxies several times during the uprising against his regime, which began exactly a year ago.

Mr Assad's media consultant told the president he had "consultations with a good number of people in addition to the media and political adviser for the Iranian ambassador" while preparing a speech in December.

The note urged the president to use "powerful and violent" language, to show appreciation for support from "friendly states" and to "leak more information related to our military capability" in order to deter protesters.

Another message from Khaled al-Ahmed, who is thought to be Assad's adviser on Homs and Idlib, pushed the president to "tighten the security grip to start (the) operation to restore state control and authority in Idlib and Hama countryside".

Other messages believed to have been sent to and from the accounts document the couple's opulent lifestyle.

One exchange between the couple appears to show the president's wife spending thousands of dollars on candlesticks, tables and chandeliers online while another reveals the leader's eclectic taste in music.