Officials in Hong Kong and Shenzhen have signed a set of seven agreements to more closely tie the two economies, the Wall Street Journal reported. Though few specific details of the accords were given, the agreements cover a range of issues including environmental protection, tourism and city planning. The two parties also said they would seek ways of bringing together the two cities not specifically covered in the pacts, including linking the cities' airports and developing a portion of the untouched land around the mainland border. Shenzhen Mayor Xu Zongheng called the accords "a new high point" in the relationship between the two cities, which some believe have seen each other as economic rivals in the past.