London - Ireland marked St Patrick's Day on Thursday with a call from political and church leaders to remember the patron saint's experience as a migrant and show sympathy for refugees in Europe.About 500 000 people were expected to watch a St Patrick's Day parade through Dublin in the afternoon, while police in Northern Ireland said officers clashed with "a drunken crowd" in Belfast in the early hours of Thursday.Archbishop Eamon Martin, head of the Catholic church in Ireland, and President Michael D Higgins led the calls to remember the plight of refugees."As Irish people, we cannot think of Patrick - the captive, the slave in exile, the undocumented, the migrant - without acknowledging the enormous humanitarian and pastoral challenges facing growing numbers of people who find themselves displaced and without status in our world," Martin said in a statement."This is so shockingly exemplified by the refugee crisis here in Europe," he said. "I ask you to pray for refugees and for all displaced families at this time."Higgins said Irish people at their best are "a nation defined by a commitment to human rights, creative imagination, and at a global level the upholding of freedom from oppression"."In this new century, we Irish have a most valuable contribution to make in the global fight against extreme poverty, hunger, and in our response to climate change," he said in a video message."Conscious of our history and culture, we can give a lead too in crafting a human response to the ongoing refugee crisis," Higgins said.In Belfast, the Police Service of Northern Ireland said officers attempted to disperse "a drunken crowd who were damaging property and throwing missiles", without further specifying what kind of projectiles were thrown.One police officer was injured and three people were arrested during the incident in Belfast's Holyland area, PSNI said in a statement.A group of around 300 people had blocked roads and sang songs supporting the Irish Republican Army, the Belfast Telegraph reported."I want everyone to enjoy the St Patrick's Day celebrations, but I would strongly encourage people to consider the long-term consequences of engaging in drunken or anti-social behaviour," PSNI Superintendent Darrin Jones said."Police will be on the streets of Belfast throughout the day to ensure anyone wishing to travel, work or socialise in Belfast can do so safely," Jones said.