* Rebels on defensive as Assad's troops counter-attack

* Rockets fired across border into Lebanon

* Military said to be airlifting troops to Aleppo (Adds fighting in Raqqa and Aleppo, Lebanon rockets)

BEIRUT, June 11 (Reuters) - Bombers attacked a Damascus police station on Tuesday, killing at least 14 people in the heart of the capital as President Bashar al-Assad's army fought rebels in their strongholds in the east and north of Syria.

Syrian state media said two suicide bombers struck near a police building in Marjeh Square, on the edge of the old city of Damascus. Syrian television had initially said the bombs were placed in bags outside shops in the square.

The British-based Syrian Observatory for Human Rights said one bomb was detonated by a suicide attacker inside the police station and the other just outside. It put the death toll at 15, most of them police.

Rebels battling to topple Assad have carried out regular bombings in the capital but are on the defensive across much of the country after a series of counter-attacks by his troops, supported near the Lebanese border by Hezbollah militants.

The pro-opposition Observatory, which monitors the conflict through a network of security and medical sources, said heavy fighting around a military base on the outskirts of rebel-held Raqqa city on Monday night resulted in the deaths of two rebel fighters.

Raqqa, on the Euphrates River in eastern Syria, was captured by rebels three months ago but they have been unable to enter the 17th Task Force Base which is resupplied by helicopter. Artillery units inside the base shell the city of Raqqa daily.

Activists also reported that military jets attacked rebel-held areas around the Minnig air base, one of Assad's last military outposts in the rural areas of Aleppo province in the north of the country.

Rebels have surrounded Minnig and captured part of the base itself, the Observatory said, but opposition activists say the army has been airlifting troops to Aleppo and reinforcing two rural Shi'ite Muslim enclaves nearby in preparation for a fresh offensive to try to reassert control in the north.

ROCKETS IN LEBANON

At least 80,000 people have been killed and more than 1.6 million refugees have fled Syria, according to the United Nations, in a conflict which pits mainly Sunni Muslim rebels against Assad, from an Alawite minority linked to Shi'ite Islam.

The sectarian battle lines have exacerbated tensions between Shi'ite and Sunni Muslims across the Middle East and spilled over into neighbouring countries including Lebanon.

Security sources said four people were wounded on Tuesday when seven rockets were fired towards the Lebanese town of Hermel, a Hezbollah stronghold in a mainly Shi'ite area of the Bekaa Valley.

The rockets appeared to have been fired from a rebel-held area across the border in Syria, they said. Syrian rebels have warned they will take the battle into Lebanon unless authorities there curb Hezbollah's involvement in the civil war.

The United Nations refugee agency UNHCR said on Tuesday it was talking to Germany about resettling up to 10,000 Syrian refugees and was working with other European governments to find ways to resettle others.

But the UNHCR, which expected the total number of refugees to more than double to 3.45 million by the end of the year, said the priority remained finding asylum for them in the region. (Reporting by Dominic Evans and Oliver Holmes in Beirut and Tom Miles in Geneva; Editing by Andrew Roche)