BEIRUT (AP) -- Syrian forces intensified their crackdown on an eastern city Sunday as they try to keep the anti-government uprising from escalating during the Muslim holy month of Ramadan. The assault and similar operations in at least two other towns killed at least 52 people, according to human rights groups, and the toll looked likely to rise.

The worst violence was in the eastern city of Deir el-Zour, where troops stepped up a siege that had already been going on for days. At least 42 people were killed in a raid on the city that began before dawn, said Abdul-Karim Rihawi, the Damascus-based chief of the Syrian Human Rights League and Ammar Qurabi, who heads the National Organization for Human Rights in Syria.

Amateur video posted online by activists showed what it said were parts of Deir el-Zour with the sound of heavy cracks of gunfire and prayers blaring from loudspeakers. Another video showed Syrian troops on a hill as they positioned an anti-aircraft gun. An activist in the city told The Associated Press the military attacked before dawn from four sides and took control of eight neighborhoods.

``Humanitarian conditions in the city are very bad because it has been under siege for nine days,'' the activist said on condition of anonymity for fear of reprisals. ``There is lack of medicine, baby formula, food and gasoline. The city is totally paralyzed.''

The attack on Deir el-Zour is part of the latest phase of the government crackdown that began a week ago, just before the start of Ramadan when many Muslims fast from dawn to dusk, then eat festive meals and gather in mosques for special nightly prayers. The government has been trying to prevent the large mosque gatherings from turning into a new wave of anti-government protests, like those that have been sweeping the country since mid-March.

The government's crackdown has left more than 1,700 dead, according to activists and human rights groups. President Bashar Assad's regime disputes the toll and blames a foreign conspiracy for the unrest.

Assad has defied the growing chorus of international condemnation and pressed on with lethal military force to suppress mostly peaceful, unarmed demonstrators. U.N. Secretary General Ban Ki-Moon urged Assad in a phone conversation on Saturday to immediately stop the use of military force against civilians.

The central city of Hama had been the focus of the crackdown for most of the past week, though Deir el-Zour has also been under siege.

In Hama, an official at Hourani Hospital reported that eight newborns died in their incubators on Wednesday when electricity was cut in the city, the London-based Syrian Observatory for Human Rights said. The group had no further details.

Authorities have imposed a media blackout on Hama and the reports could not be immediately confirmed. Electricity, Internet and phone lines have been cut for seven days, and residents have reported dwindling food and medical supplies amid frequent shelling and raids. Rights group say at least 100 people have been killed, while some estimates put the number as high as 250.

The military attacks also spread Sunday to the central town of Houleh in Homs province, about 30 miles (50 kilometers) south of Hama and 212 miles (340 kilometers) east of Deir el-Zour. Rihawi said at last 10 people were killed in Houleh while Qurabi said the toll was 17.

Both Houleh and Deir el-Zour have witnessed intense protests against Assad since the uprising began. Deir el-Zour is the capital of an oil-rich province by the same name, but the region is among the country's poorest and was hit by drought in the past years. It is inhabited by Arab tribes that extend into Iraq, and Syrian authorities have said they thwarted attempts by Iraqis to smuggle arms from Iraq into Syria.

Qurabi said security forces also shot and killed 10 people in the northwestern city of Idlib Sunday. He said those killed in Idlib were taking part in a funeral of eight protesters shot dead by security forces Saturday night in the city.

Rihawi had no figures from Idlib but the Local Coordination Committees, a key activist groups tracking the Syrian uprising, said at least four people were shot dead in Idlib when security forces opened fire at a funeral.

In Hama, state-run news agency SANA said troops removed all barriers and roadblocks in the main streets, but continued ``to chase remains of terrorists'' who took positions in two neighborhoods.

SANA claimed anti-regime gunmen in the city had killed 13 policemen whose bodies were removed Saturday from the Orontes River, which runs through Hama. An amateur video posted online by government supporters last week showed men throwing what it said were dead plainclothes policemen's bloody bodies from a bridge into the river, turning the water to a red stream.

Turkey, which borders Syria, said Sunday it would send its foreign minister to Damascus on Tuesday to deliver a strong message condemning the crackdown on the protesters. Turkish Prime Minister Recep Tayyip Erdogan said his country's patience was running thin and that Turkey could not remain a bystander to the violence.

Syria's reaction was quick. State-run TV quoted Assad's adviser, Buthaina Shaaban, as saying that Turkey's foreign minister ``will hear stronger words because of Turkey's stance that did not condemn until now the brutal killings of civilians, members of military and police.''

Gulf Arab countries broke their silence Saturday on the bloodshed, calling for an immediate end to the violence and for the implementation of ``serious'' reforms in Syria. In a statement posted on its website, the six-nation Gulf Cooperation Council expressed deep concern and regret for ``the escalating violence in Syria and use of excess force.''

Syria's state-run TV quoted an unnamed official as saying the GCC statement was ignoring the sabotage that armed groups are conducting.

Assad again promised to pursue reforms, SANA reported, something he has promised before but failed to deliver.