China's main newspaper accused Western countries of stirring civil war in Syria and two Iranian warships docked at a Syrian naval base, underscoring rising international tensions over the near year-long crisis.

Despite a continued government crackdown on the opposition in cities across the country, President Bashar al-Assad forged ahead with plans to hold a referendum at the end of the week.

Syrian government forces maintained their siege of pro-opposition neighbourhoods of Homs, a western city at the heart of the revolt. Opposition activists reported sporadic morning shelling of Baba Amro district.

Security forces also mounted a campaign of arrests and raids in two suburbs of Deraa city and loud gunfire was heard, activists said. The reports could not be independently verified.

The Monday morning action followed a weekend which saw one of the biggest anti-Assad demonstrations yet in the capital as the pro-democracy uprising against his 11 year-rule neared its first anniversary.

Security forces have killed at least 5,000 people, according to human rights groups, in a campaign to crush the revolt while the Assad government says it has lost more than 2,000 soldiers and security agents in what it describes as a struggle against foreign-backed terrorists,

The conflict has also pitted Western and Gulf-led Arab powers against Assad allies Russia, China and Iran.

The former have condemned Assad for the bloodshed and called for him to step down. Beijing and Moscow say all sides are to blame for the violence and the crisis should be resolved through talks, not foreign intervention.

China's Communist Party mouthpiece the People's Daily, in a front page commentary on Monday, said: If Western countries continue to fully support Syria's opposition, then in the end a large-scale civil war will erupt and there will be no way to thus avoid the possibility of foreign armed intervention.

A Chinese envoy met Assad in Damascus on Saturday and backed his plan to hold a referendum this coming Sunday on a new constitution which would lead to multi-party parliamentary elections with 90 days.

Syria's official SANA news agency said about 14,600,000 people throughout Syria were eligible to take part in the referendum.

Deputy Minister of Interior for Civil Affairs, General Hassan Jalali said 13,835 offices were devoted to the poll, including ones opened on land borders and at airports to enable all citizens to vote.

The West and Syrian opposition figures have dismissed the plan as joke, saying it is impossible to have valid election amid the continuing repression.

WESTERN FEARS

Assad has ruled Syria for 11 years after succeeding his father Hafez on his death. The Assad family belongs to the Alawite sect, an offshoot of Shi'ite Islam, in a majority Sunni country, and there are fears the uprising could break down into a full sectarian conflict.

Foreign ministers at a G20 industrialised and emerging nations meeting in Mexico were increasingly worried about whether a peaceful solution could be found.

There is grave concern about the fact that existing structures of the United Nations have not delivered an outcome,

Australia's foreign minister, Kevin Rudd, told reporters in Los Cabos, Mexico.

The West has ruled out any Libya-style military intervention but the Arab League, led by Saudi Arabia, has indicated some of its member states were prepared to arm the opposition.

In Washington the senior U.S. military officer, General Martin Dempsey, said intervening in Syria would be very difficult because it was not like Libya.

Syria's army is very capable, with a sophisticated, integrated air defence system and chemical and biological weapons, Dempsey said. It was also not clear who or what the fragmented opposition was exactly, he said.

IRANIAN SHIPS

Meanwhile two Iranian naval ships docked at the Syrian port of Tartous on Saturday, Iran's state-run Press TV reported. The ships were said to be providing training for Syrian naval forces under an agreement signed a year ago.

Iranian Defence Minister Ahmad Vahidi, quoted by the semi-official Fars news agency, said: Our ships passed through the Suez canal and it is Iran's right to have a presence in international waters.

With Shi'te-led Iran already at odds with the United States, Europe and Israel over its nuclear programme, the deployment was

likely to add to Western concerns that the Syria crisis could boil over into a regional conflict if it not resolved soon.

A so-called Friends of Syria conference is scheduled to take place in Tunisia this Friday, bringing together Western and Arab powers. The group was formed at the instigation of France and the United States after Russia and China shot down a proposed resolution at the U.N. Security Council calling for Assad to relinquish power.

Australia's Rudd, speaking in Mexico, said the group aims to place maximum pressure on president Assad to go, to end the butchery that we see day by day unfolding in Syria and to make sure we have a durable and peaceful political transition.

(Additional reporting by Khaled Yacoub Oweis in Amman, Parisa Hafezi in Tehran; Susan Cornwell in Washington; Krista Hughes in Los Cabos, Mexico; Editing by Giles Elgood)