To Naphkhororia [Akhenaten] King of Egypt, my brother, to say: Thus speaks Burnaburiash King of Babylon, your brother. I am well. To your country, your house, your women, your sons, your ministers, your horses, your chariots, many greetings. I and my brother have signed a treaty, and I spoke thus: Like our fathers, who were friends, we will be friends. And now, my merchants who travelled with Ahutabu delayed in Canaan for business. After Ahutabu set out on his way to my brother and in the town of Hanatun which is in Canaan Shumda son of Baluma and Shutatna son of Shartum from Akko sent their men there. They beat my merchants and stole their money. Ahutabu, whom I sent to you, is before you. Ask him and he will tell you. Canaan is your country and its kings are your slaves, in your country I was robbed. Bind them and return the money they robbed. And the men who murdered my slaves, kill them and avenge their blood. Because if you do not kill these men, they will again murder my caravans and even my ambassadors, and the ambassadors between us will cease. If this should happen the people of the land will leave you.
-Letter of Burnaburiash II to Akhenaten, from the Amarna Archives, EA 8.
The Amarna Letters are an archive of diplomatic correspondence inscribed on clay tablets during the late Eighteenth Dynasty of Egypt (mid to late fourteenth century BCE). They are inscribed mostly in Akkadian, a Semitic language that served as a diplomatic and mercantile lingua franca in the Bronze Age Middle East (just as Greek, Latin and French would serve the same purpose in late antiquity, the Middle Ages, and the early modern period). The letters, mostly discovered between 1887 and 1903 in the ruins of Akhetaten (modern Tel el-Amarna, for which the letters are named), give a fascinating window into the economics and politics of the ancient Middle East.
The period of the Amarna Letters appears to have been a relatively peaceful one (at least compared to the immediately preceding and subsequent decades) in which the Middle East was dominated by a number of great powers: The New Kingdom of Egypt, the Hurrian kingdom of Mittani (northeastern Syria and southern Anatolia), the nascent Hittite Empire (central Anatolia), the Kassite dynasty of Babylon (southern Mesopotamia), the Middle Assyrian Empire (northern Mesopotamia), and Alashiya (Cyprus). The spaces between these great powers were filled with hundreds of chiefdoms and city-states for whose loyalty the major kingdoms competed. A large body of Amarna letters are correspondence between the Pharaohs Amenhotep III and his successor Akhenaten with various client-kings in Canaan and southern Syria, while others are diplomatic missives between the Egyptian court and its counterparts in the other "great-power" states.
In the above-quoted excerpt from EA 8 (scholars designate the letters by a universally-accepted numbering scheme), Burnaburiash, the king of Babylon, reports an attack on Babylonian merchents in the city of Akko, a Canaanite city and Egyptian vassal. In simple and stark terms, Burnaburiash sets out claims for both business tort and criminal claims, and seeks both monetary restitution and punitive action against the attackers. EA 8 and other letters in the Amarna archive reflect the early development of international law and regulation governing trade.
A concordence of terms appearing in the Amarna letters can be found here.
For general information online, the following sources are useful:
Academia.edu has a large body of articles available for free on the topic, which can be found here.
For further reading, see, e.g., William L. Moran, The Amarna Letters (Johns Hopkins Univ. Press, 2000); Raymond Cohen, et al., Amarna Diplomacy: The Beginnings of International Relations (Johns Hopkins Univ. Press, 2002).