FREETOWN (Reuters) - Artillery fire shook the Sierra Leone capital Freetown on Monday and Nigerian-led peacekeepers said they had repelled a rebel attack on the city‘s Hastings Airport. "The rebels attacked Hastings at about 3.00 a.m. (0300 GMT) this morning, but we have now beaten them back into the hills around the town," Colonel Jimoh Okunlola, spokesman for the West African intervention force ECOMOG told Reuters. He said ECOMOG, backed by a loyalist militia, was mopping up the area around Hastings, on the eastern outskirts of the capital. Okunlola said dozens of rebels were killed but gave no casualty figure for the peacekeepers. ECOMOG troops intensified checks at roadblocks in Freetown and tension rose again in the city just as residents were enjoying some quiet after weekend clashes on the outskirts. Last week Nigeria reinforced its troops, who are the bulwark of ECOMOG, boosting the force‘s numbers to between 15,000 and 19,000, according to ECOMOG sources. ECOMOG includes contingents from Ghana and Guinea. Gambia and Mali have agreed to send troops to the force, set up by the 16-nation Economic Community of West African States. The insurgents are renegade soldiers and guerrillas loyal to a military junta evicted from Freetown by ECOMOG last February, 10 months after a coup against President Ahmad Tejan Kabbah. ECOMOG reinstated Kabbah in March but rebels regrouped and launched a new campaign after their leader, Foday Sankoh, was sentenced to death for treason in October. Sankoh, in detention in Freetown, is appealing against the sentence. Regional efforts to resolve the conflict peacefully have failed so far, with Kabbah demanding that rebels first lay down their arms and the guerrillas insisting on Sankoh‘s release. Rebels launched a more serious attack on Hastings last Friday in an attempt to take the country‘s main domestic airport and the main base for Nigerian and Ghanaian ECOMOG troops. At least 10 buildings were burned in the attack. The fighting closed the airport, which was due to reopen on Monday. State radio said on Monday that some members of a U.N. observer mission evacuated last week as rebels attacked close to the capital returned on Saturday. More were expected to return on Monday as ECONOG had beaten back the rebels. The last reported fighting before the Hastings clashes was on Saturday around Port Lokmo, 35 miles (50 km) northeast of Freetown on a main highway to neighbouring Guinea. As a result of the fighting there, thousands of people, both Sierra Leonean and Guinean, fled to the area near the border with Guinea.