SARAJEVO Oct 9. The In tematlonal airlift that keeps Sarajevo alive resumed Sunday bringing aid to a mourning city with only three days supplies left, reports AP

In an effort to built up supplies ahead of winter and a possible Serb shutdown of the airport. 19 UN aid flights and two Red Cross planes were scheduled Planes from Anco na, Italy and Split. Croatia, began touching down at Sara jevo airport Sunday morning.

The resumption ot aid fol lowed a sniper attack on trams In central Sarajevo Saturday which killed one num and wounded I I Including live children

Pools of blood stained pavement and two of the empty trams. U N spokesman Koos Sol said the fire ap,»r ently came from Bosnian Serb positions

The airlift whi< h provides

about 80 per cent of the city's food, was suspended Saturday just a day after ft was restarted following a two week shut -down Forces from both war ring sides each fired on planes Friday but no one was Injured. Sol said.

• UN officials reached agree ment Saturday with the Muslim-led Bosnian govern ment and the Serbs on seen rity at the airport, said another UN spokesman. Maj Herve Gourmelon.

Angered over a NATO air strike on one of their tanks Sept 22. Serb troops had blocked UN movements and kept the Sarajevo airport closed with threats to shoot st planes

On Friday, Bosnian Serbs refused to give clearance tor a convoy carrying nearly 100 tons of food to Sarajevo The last food convoy to reach the Bosnian capital arrived the day

of the air strike

Kris Janowski, a spokesman for the United Nations High < ommissfoner for Refugees In Sarajevo, said there were only enough rations in the city to last three days

On Mount Ignian. southwest of Sarajevo, peacekeepers cleared more than 500 Bos nlan government soldiers out of .i demilitarised zone near where 20 Serbs were killed Thursday In a commando raid, (heir ^hroats apparently slit

The Muslim led govern ment confirmed that tts sol dlers killed the Serbs tn a commando attack.

A Bosnian Serb leader, furious over the slayings, de mended the UN prove Its im l>artialltv by punishing the guv ernmrnf

II the I IN doesn't do It we will Momcilo Kiajlsnlk (old i be Bosnian Serb news agency SRNA

UN spokesman Pau) Risley said in Zagreb. Croatia, that the Bosnian Serbs said they would answer by Wednesday whether they will keep coop erating with « the United Nations

The Wednesday deadline made UN officials anxious to get as much aid into Sarajevo as possible in case the airport again shuts down UN officials are dependent on Serb assur ancss of safety (o work in Serb held Bosnia and in Serb sur rounded Sarajevo

Bosnian government offt cials also attacked the United Nations, citing the snipping attack as another example of Its alleged Inaction.

The Bosnian war began In April. 1992. when Serbs re Ijelled against a decision to se cede from Serb dominated Yugoslavia About 200.000 people are dead or missing