ISMAILIA, Egypt, Aug 19 (Reuters) - Egyptian police shot dead a 27-year-old Sudanese man as he tried to slip over the border into Israel, security officials said on Tuesday.

The killing, which officials said took place at night on Monday, brings to 20 the number of African migrants killed at the border so far this year.

A police patrol saw the Sudanese man and four other migrants attempting to get through barbed wire on the border and ordered them to stop, opening fire when they failed to do so.

Police arrested two of the migrants, while the remaining two managed to escape towards Egypt.

For years Egypt tolerated tens of thousands of African migrants in its territory but the situation changed in recent months and border violence has escalated as the government cracked down on the migrants.

The Africans, mainly Sudanese and Eritrean, are seeking work or asylum away from conflict at home and harsh living conditions in Egypt, where activists say African migrants face economic marginalisation and racism.

On Monday an Egyptian policeman was shot and killed by traffickers trying to take a group of migrants into Israel. He was the third policemen killed this year in clashes with traffickers. (Reporting by Yusri Mohamed, writing by Aziz El-Kaissouni, editing by Alaa Shahine and Mary Gabriel)